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.
Problem types
CWE-116 Improper Encoding or Escaping of Output
Product status
Any version before 1.7.0
Any version before 1.7.0
Any version before 1.7.0
Timeline
| 2026-03-15: | Vulnerability reported by Olawale Titiloye |
| 2026-03-16: | Fix shared publicly by Stephen Webb as pull request #609 |
| 2026-04-04: | Log4cxx 1.7.0 released |
Credits
Olawale Titiloye
References
www.openwall.com/lists/oss-security/2026/04/10/12
github.com/apache/logging-log4cxx/pull/609
logging.apache.org/security.html
logging.apache.org/cyclonedx/vdr.xml
logging.apache.org/.../classlog4cxx_1_1xml_1_1XMLLayout.html
lists.apache.org/thread/y15cv3zblg3dfwr5vy6ddbnl4zyrzr8b