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[ CVE-2021-45046 · Published 14 Dec 2021 ]

Apache Log4j2 Deserialization of Untrusted Data Vulnerability

Exploited · CISA KEV CVSS 9.0 EPSS 100%Fix available

[ Why it matters ]Priority signals

  • Exploited in the wild: on CISA's Known Exploited Vulnerabilities list since 2023-05-01
  • Known to be used in ransomware campaigns
  • EPSS: 100% chance of exploitation in the next 30 days (higher than 100% of CVEs)
  • Critical severity: CVSS 9.0

[ Description ]Official description

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.

CISA: Apache Log4j2 contains a deserialization of untrusted data vulnerability due to the incomplete fix of CVE-2021-44228, where the Thread Context Lookup Pattern is vulnerable to remote code execution in certain non-default configurations.

[ Fixes ]Fixes and patches

CISA required action (US federal deadline 22 May 2023): Apply updates per vendor instructions.

[ References ]References