Riskcovery

CVE-2026-40023

Apache Log4cxx, Apache Log4cxx (Conan), Apache Log4cxx (Brew): Silent log event loss in XMLLayout due to unescaped XML 1.0 forbidden characters

State
Published
Severity
6.3 Medium
Published
Apr 10, 2026
Updated
Apr 10, 2026
Reserved
Apr 8, 2026

Read the record on cve.org

Description

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.

Scores

CVSSScoreVectorSource
4.06.3 MediumCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:Napache

Weaknesses

  • CWE-116 Improper Encoding or Escaping of Output

Affected Products

ProductVersions
Apache Log4cxxApache Software Foundation
  • before 1.7.0Affected
Apache Log4cxx (Conan)Apache Software Foundation
  • before 1.7.0Affected
Apache Log4cxx (Brew)Apache Software Foundation
  • before 1.7.0Affected

References

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