CRLF Injection Affecting log4j:2/log4j package, versions *


Severity

Recommended
0.0
medium
0
10

Based on Red Hat Enterprise Linux security rating.

Threat Intelligence

EPSS
0.14% (35th percentile)

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  • Snyk IDSNYK-RHEL8-LOG4J-16075243
  • published15 Apr 2026
  • disclosed10 Apr 2026

Introduced: 10 Apr 2026

NewCVE-2026-34478  (opens in a new tab)
CWE-93  (opens in a new tab)

How to fix?

There is no fixed version for RHEL:8 log4j:2/log4j.

NVD Description

Note: Versions mentioned in the description apply only to the upstream log4j:2/log4j package and not the log4j:2/log4j package as distributed by RHEL. See How to fix? for RHEL:8 relevant fixed versions and status.

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.

CVSS Base Scores

version 3.1