CVEvulnerability

CVE-2026-34478

6.9 MEDIUM Published 2026-04-10 Modified 2026-10-26 Official page ↗
Status
Analyzed
Published
2026-04-10
Last modified
2026-10-26
Assigner
[email protected]
CVSS 4.0 ([email protected])
6.9 MEDIUM — CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CVSS 3.1 ([email protected])
7.5 HIGH — CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Weaknesses
CWE-117, CWE-684

Description

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.

Affected configurations

• apache log4j (>= 2.21.0 < 2.25.4) • apache log4j 3.0.0

Related

Weakness · CWE (2)

  • CWE-117 Improper Output Neutralization for Logs weakness
  • CWE-684 Incorrect Provision of Specified Functionality weakness

References