The fix to address CVE-2021-44228 in Apache Log4j 2.15.0 was incomplete in certain non-default configurations. This could allow 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 a remote code execution (RCE) attack.
Only the org.apache.logging.log4j:log4j-core
package is directly affected by this vulnerability. The org.apache.logging.log4j:log4j-api
should be kept at the same version as the org.apache.logging.log4j:log4j-core
package to ensure compatability if in use.
Log4j 2.16.0 fixes this issue by removing support for message lookup patterns and disabling JNDI functionality by default. This issue can be mitigated in prior releases (< 2.16.0) by removing the JndiLookup class from the classpath (example: zip -q -d log4j-core-*.jar org/apache/logging/log4j/core/lookup/JndiLookup.class).
Log4j 2.15.0 restricts JNDI LDAP lookups to localhost by default. Note that previous mitigations involving configuration such as to set the system property log4j2.formatMsgNoLookups
to true
do NOT mitigate this specific vulnerability.
{ "nvd_published_at": "2021-12-14T19:15:00Z", "cwe_ids": [ "CWE-502", "CWE-917" ], "severity": "CRITICAL", "github_reviewed": true, "github_reviewed_at": "2021-12-14T17:55:00Z" }