Severity: moderate (CVSS: 3.7 AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L)
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 a
denial of service (DOS) attack. 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.noFormatMsgLookup` to `true` do NOT
mitigate this specific vulnerability.
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).
References:
https://logging.apache.org/log4j/2.x/security.html
https://www.cve.org/CVERecord?id=CVE-2021-44228
