Bug 2457323 (CVE-2026-34478) - CVE-2026-34478 org.apache.logging.log4j/log4j-core: Apache Log4j Core: Log injection via CRLF sequences due to configuration attribute renames
Summary: CVE-2026-34478 org.apache.logging.log4j/log4j-core: Apache Log4j Core: Log in...
Keywords:
Status: NEW
Alias: CVE-2026-34478
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
medium
medium
Target Milestone: ---
Assignee: Product Security DevOps Team
QA Contact:
URL:
Whiteboard:
Depends On: 2457896 2457899 2457900 2457895 2457897 2457898
Blocks:
TreeView+ depends on / blocked
 
Reported: 2026-04-10 16:02 UTC by OSIDB Bzimport
Modified: 2026-05-15 17:58 UTC (History)
71 users (show)

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Description OSIDB Bzimport 2026-04-10 16:02:16 UTC 
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.
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