CVE-2021-45046

CVE-2021-45046 is a critical-severity (CVSS 9.0) vulnerability in Apache Log4j2. CISA added it to the Known Exploited Vulnerabilities catalog on May 1, 2023, which means exploitation in the wild has been confirmed; US federal agencies had to remediate it by May 22, 2023. CISA also lists it as known to be used in ransomware campaigns, so it should be prioritised accordingly. Apache has 41 vulnerabilities in the KEV catalog, 8 of them linked to ransomware.

It was found that the fix to address CVE-2021-44228 in Apache Log4j 2.15.0 was incomplete in certain non-default configurations. This could allows attackers with control over Thread Context Map (MDC) input data when the logging configuration uses a non-default Pattern Layout with either a Context Lookup (for example, $${ctx:loginId}) or a Thread Context Map pattern (%X, %mdc, or %MDC) to craft malicious input data using a JNDI Lookup pattern resulting in an information leak and remote code execution in some environments and local code execution in all environments. Log4j 2.16.0 (Java 8) and 2.12.2 (Java 7) fix this issue by removing support for message lookup patterns and disabling JNDI functionality by default.

CVSS vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H

• http://www.openwall.com/lists/oss-security/2021/12/14/4
• http://www.openwall.com/lists/oss-security/2021/12/15/3
• http://www.openwall.com/lists/oss-security/2021/12/18/1
• https://cert-portal.siemens.com/productcert/pdf/ssa-397453.pdf
• https://cert-portal.siemens.com/productcert/pdf/ssa-479842.pdf
• https://cert-portal.siemens.com/productcert/pdf/ssa-661247.pdf
• https://cert-portal.siemens.com/productcert/pdf/ssa-714170.pdf
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/EOKPQGV24RRBBI4TBZUDQMM4MEH7MXCY/