The Log4j saga: New vulnerabilities and attack vectors discovered
Vulnerabilities mentionedAll →
| CVE | Vulnerability | CVSS | EPSS | Flags | Affected | Exposure | Published |
|---|---|---|---|---|---|---|---|
| CVE-2021-4104 | JMSAppender in Log4j 1.2 is vulnerable to deserialization of untrusted data when the attacker has write access to the Log4j configuration. JMSAppender in Log4j 1.2 is vulnerable to deserialization of untrusted data when the attacker has write access to the Log4j configuration. The attacker can provide TopicBindingName and TopicConnectionFactoryBindingName configurations causing JMSAppender to perform JNDI requests that result in remote code execution in a similar fashion to CVE-2021-44228. Note this issue only affects Log4j 1.2 when specifically configured to use JMSAppender, which is not the default. Apache Log4j 1.2 reached end of life in August 2015. Users should upgrade to Log4j 2 as it addresses numerous other issues from the previous versions. NVD description · AI analysis pending | 7.5 | 81% |
| — | ||
| CVE-2021-44228 | JNDI Injection Remote Code Execution in Apache Log4j2 (Log4Shell) Apache Log4j2, an extremely widely used Java logging library, fails to protect its JNDI lookup feature against attacker-controlled JNDI-related endpoints (CWE-20, CWE-502), so crafted text processed by the logger causes the Java runtime to fetch and load attacker-supplied objects, leading to remote code execution. The flaw is triggered whenever attacker-controlled input reaches the logging API and is parsed for JNDI lookups, a pattern common in web servers and enterprise Java applications that log user-supplied fields such as headers or form values. Successful exploitation yields arbitrary code execution under the privileges of the affected application, giving attackers a foothold for lateral movement, data theft, and ransomware deployment. Any Java application or product that ships or bundles an affected Apache Log4j2 release is exposed, making this one of the most broadly deployed vulnerabilities ever disclosed. Exploitation is confirmed in the wild: CISA added it to the Known Exploited Vulnerabilities catalog on 2021-12-10 with known ransomware use, and EPSS assigns a 100% probability of exploitation within 30 days. Do: Inventory all Java applications and dependencies for Apache Log4j2 and apply the vendor's patched updates, or remove affected assets from the network, as required by CISA's KEV catalog. Where updates are not yet available, use the temporary mitigations in CISA's ED-22-02 recommended-mitigation guidance, such as disabling message lookups, only until patches are applied. Prioritize internet-facing and business-critical systems and hunt for exploitation activity given known ransomware use. | 10.0 | 100% | KEV ransomware PoC ×9 |
| masshundreds of millions of Java applications/devices, with hundreds of thousands of internet-exposed services | |
| CVE-2021-45046 | Remote Code Execution in Apache Log4j2 via Incomplete Log4Shell Fix CVE-2021-45046 is a remote code execution and information disclosure flaw in Apache Log4j2 (CWE-917) that resulted from an incomplete fix to CVE-2021-44228 (Log4Shell), leaving the Thread Context Lookup Pattern vulnerable in certain non-default configurations. It is triggered when an application logs attacker-controlled data using layouts or patterns that perform Thread Context (MDC) lookups, allowing crafted lookup expressions to be evaluated against untrusted input. A successful attacker can achieve remote code execution, or potentially information disclosure, on the affected service. Any deployment of Apache Log4j2 that relies on the affected non-default lookup configurations is exposed, which given Log4j2's ubiquity in Java applications and embedded products means a very large installed base. Exploitation is confirmed: the flaw is in CISA KEV (added 2023-05-01) with known ransomware use, and EPSS assigns a 100% probability of exploitation within 30 days. Do: Upgrade Log4j2 to 2.17.0 or later per vendor instructions (or 2.12.3/2.3.1 for the legacy 2.12/2.3 branches), since the 2.16.0 fix was itself incomplete in some non-default configurations. Where upgrading is not immediately possible, remove the JndiLookup class from the Log4j2 jar or disable lookup processing, and audit applications and dependencies that bundle Log4j2 while following the CISA KEV required action to apply vendor updates. | 9.0 | 100% | KEV ransomware |
| massmillions of Java deployments worldwide, with hundreds of thousands of internet-exposed services observed in public scans during the Log4Shell campaign | |
| CVE-2021-45105 | Apache Log4j2 versions 2.0-alpha1 through 2.16.0 (excluding 2.12.3 and 2.3.1) did not protect from uncontrolled recursion from self-referential lookups. Apache Log4j2 versions 2.0-alpha1 through 2.16.0 (excluding 2.12.3 and 2.3.1) did not protect from uncontrolled recursion from self-referential lookups. This allows an attacker with control over Thread Context Map data to cause a denial of service when a crafted string is interpreted. This issue was fixed in Log4j 2.17.0, 2.12.3, and 2.3.1. NVD description · AI analysis pending | 5.9 | 100% |
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Full article675 words · extracted from helpnetsecurity.com · click to collapse
The Apache Log4j saga continues, as several new vulnerabilities have been discovered in the popular library since Log4Shell (CVE-2021-44228) was fixed by releasing Log4j v2.15.0.
There’s CVE-2021-45046, a DoS/RCE flaw that was fixed in v2.16.0, then CVE-2021-45105, a DoS hole plugged in v2.17.0. Oh, and there’s CVE-2021-4104, a RCE vulnerability affecting Log4j v1.2, which will not be fixed because the 1.x branch has reached end-of-life.
But these new revelations should not make you panic. While Log4Shell is exploitable in the default configuration of the library, the others are not, and the likelihood of those getting exploited is, according to Tenable‘s Satnam Narang, low.
Security threat analyst Kevin Beaumont concurs:
Log4j hype check – the latest Log4j vulnerability, todays CVE-2021-45105:
– only applies to *non-default* configurations
– would only allow the Java process to terminate, no code execution.Focus on remediating Log4Shell and do not get caught in the vulnerability hype train.
— Kevin Beaumont (@GossiTheDog) December 18, 2021
There is going to be continued focus on log4j vulns for some time. It is very important to know not every new vulnerability is equal, or likely to be exploited.
— Kevin Beaumont (@GossiTheDog) December 19, 2021
So, if possible, organizations should upgrade all the Log4j instances to v2.17.0 (for Java 8) and v2.12.2 (For Java 7). If that’s not possible, the project maintainers advise removing the JndiLookup class from the classpath.
The CISA has issued on Friday an emergency directive mandating federal civilian executive branch agencies to address Log4j vulnerabilities by December 28, 2021.
Affected products
As some companies elatedly confirm their products are not affected by the flaws because they don’t use the Log4j library, Google has scanned Maven Central, the most significant Java package repository, and found that over 35,000 available Java artifacts depend on the affected log4j code.
“Direct dependencies account for around 7,000 of the affected artifacts, meaning that any of its versions depend upon an affected version of log4j-core or log4j-api, as described in the CVEs. The majority of affected artifacts come from indirect dependencies (that is, the dependencies of one’s own dependencies), meaning log4j is not explicitly defined as a dependency of the artifact, but gets pulled in as a transitive dependency,” James Wetter and Nicky Ringland of Google’s Open Source Insights Team explained.
“At the time of writing, nearly five thousand of the affected artifacts have been fixed. This represents a rapid response and mammoth effort both by the log4j maintainers and the wider community of open source consumers. That leaves over 30,000 artifacts affected, many of which are dependent on another artifact to patch (the transitive dependency) and are likely blocked.”
The Dutch Nationaal Cyber Security Centrum (NCSC-NL) and the CISA are constantly updating their lists of affected products.
Log4j attack vectors
Alternative Log4Shell attack vectors are getting discovered. This one, documented by Blumira researchers, could trigger the RCE on internal and locally exposed unpatched Log4j applications.
According to AdvIntel researchers Vitali Kremez and Yelisey Boguslavskiy, the Conti ransomware gang has started using the Log4Shell bug for lateral movement.
“The current exploitation led to multiple use cases through which the Conti group tested the possibilities of utilizing the Log4J2 exploit. Most importantly, AdvIntel confirmed that the criminals pursued targeting specific vulnerable Log4J2 VMware vCenter for lateral movement directly from the compromised network resulting in vCenter access affecting US and European victim networks from the pre-existent Cobalt Strike sessions,” they shared.
Risk mitigation
Time is of the essence.
“It is only a matter of time until Conti and possibly other groups will begin exploiting Log4j2 to its full capacity. It is recommended to patch the vulnerable system immediately and view the Log4j2 as a ransomware group exploitation vector,” the AdvIntel researchers noted.
Administrators of OT networks should also be actively working on finding and implementing solutions to protect them against exploitation.
The advice for board members that the UK’s National Cyber Security Centre has published on Friday is a helpful primer on what organizations should be doing at the moment.
Text extracted automatically; images, tables and formatting may be missing. Original: https://www.helpnetsecurity.com/2021/12/20/log4j-attack-vectors/