Improper Output Neutralization for Logs Affecting log4cxx package, versions *


Severity

Recommended
0.0
medium
0
10

Based on Red Hat Enterprise Linux security rating.

Threat Intelligence

EPSS
0.5% (39th percentile)

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  • Snyk IDSNYK-RHEL7-LOG4CXX-16076189
  • published15 Apr 2026
  • disclosed10 Apr 2026

Introduced: 10 Apr 2026

CVE-2026-40023  (opens in a new tab)
CWE-117  (opens in a new tab)

How to fix?

There is no fixed version for RHEL:7 log4cxx.

NVD Description

Note: Versions mentioned in the description apply only to the upstream log4cxx package and not the log4cxx package as distributed by RHEL. See How to fix? for RHEL:7 relevant fixed versions and status.

Apache Log4cxx's XMLLayout https://logging.apache.org/log4cxx/1.7.0/classlog4cxx_1_1xml_1_1XMLLayout.html , in versions before 1.7.0, fails to sanitize characters forbidden by the XML 1.0 specification https://www.w3.org/TR/xml/#charsets in log messages, NDC, and MDC property keys and values, producing invalid XML output. Conforming XML parsers must reject such documents with a fatal error, which may cause downstream log processing systems to drop or fail to index affected records.

An attacker who can influence logged data can exploit this to suppress individual log records, impairing audit trails and detection of malicious activity.

Users are advised to upgrade to Apache Log4cxx 1.7.0, which fixes this issue.

CVSS Base Scores

version 3.1