Apache Log4j Core: Log injection in Rfc5424Layout due to silent configuration incompatibility
Summary
Apache Log4j Core: Log injection in Rfc5424Layout due to silent configuration incompatibility
Original description
The description as published by the source.
Apache Log4j Core's Rfc5424Layout https://logging.apache.org/log4j/2.x/manual/layouts.html#RFC5424Layout , in versions 2.21.0 through 2.25.3, is vulnerable to log injection via CRLF sequences due to undocumented renames of security-relevant configuration attributes.
Two distinct issues affect users of stream-based syslog services who configure Rfc5424Layout directly:
- The newLineEscape attribute was silently renamed, causing newline escaping to stop working for users of TCP framing (RFC 6587), exposing them to CRLF injection in log output.
- The useTlsMessageFormat attribute was silently renamed, causing users of TLS framing (RFC 5425) to be silently downgraded to unframed TCP (RFC 6587), without newline escaping.
Users of the SyslogAppender are not affected, as its configuration attributes were not modified.
Users are advised to upgrade to Apache Log4j Core 2.25.4, which corrects this issue.
Source: OSV.dev (Open Source Vulnerabilities) NVD GitHub Advisory OSV
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Ubuntu UBUNTU-CVE-2026-34478 apache-log4j1.2
References
- advisory github.com
- advisory lists.apache.org
- advisory logging.apache.org
- advisory logging.apache.org
- advisory nvd.nist.gov
- patch github.com
- web openwall.com
- web logging.apache.org
- web repo.maven.apache.org