CVEvulnerability
CVE-2026-40023
6.3 MEDIUM
Official page ↗
- Status
- Analyzed
- Published
- 2026-04-10
- Last modified
- 2026-10-26
- Assigner
- [email protected]
- CVSS 4.0 ([email protected])
- 6.3 MEDIUM — CVSS:4.0/AV:N/AC:H/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])
- 5.3 MEDIUM — CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
- Weaknesses
- CWE-116
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.
Affected configurations
• apache log4cxx (< 1.7.0)
Related
Weakness · CWE (1)
- CWE-116 Improper Encoding or Escaping of Output weakness
References
- https://github.com/apache/logging-log4cxx/pull/609 Issue Tracking, Patch
- https://lists.apache.org/thread/y15cv3zblg3dfwr5vy6ddbnl4zyrzr8b Mailing List, Vendor Advisory
- https://logging.apache.org/cyclonedx/vdr.xml Product
- https://logging.apache.org/log4cxx/1.7.0/classlog4cxx_1_1xml_1_1XMLLayout.html Product
- https://logging.apache.org/security.html#CVE-2026-40023 Vendor Advisory
- http://www.openwall.com/lists/oss-security/2026/04/10/12 Mailing List, Third Party Advisory