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.
Metrics
CVSS 3.1 5.3/10
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:NWeakness enumeration
Affected software
| Vendor | Product | Versions |
|---|---|---|
| Apache Software Foundation | Apache Log4cxx | < 1.7.0 |
| Apache Software Foundation | Apache Log4cxx (Conan) | < 1.7.0 |
| Apache Software Foundation | Apache Log4cxx (Brew) | < 1.7.0 |
References
- https://github.com/apache/logging-log4cxx/pull/609Issue Tracking, Patch
- https://lists.apache.org/thread/y15cv3zblg3dfwr5vy6ddbnl4zyrzr8bMailing List, Vendor Advisory
- https://logging.apache.org/cyclonedx/vdr.xmlProduct
- https://logging.apache.org/log4cxx/1.7.0/classlog4cxx_1_1xml_1_1XMLLayout.htmlProduct
- https://logging.apache.org/security.html#CVE-2026-40023Vendor Advisory
- http://www.openwall.com/lists/oss-security/2026/04/10/12Mailing List, Third Party Advisory
Timeline
- Published
- Apr 10, 2026
- Last modified
- Oct 26, 2026
- NVD status
- Analyzed