| Name | CVE-2026-40023 |
| 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. |
| Source | CVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more) |
The table below lists information on source packages.
| Source Package | Release | Version | Status |
|---|---|---|---|
| log4cxx (PTS) | bullseye | 0.11.0-2 | vulnerable |
| bullseye (security) | 0.11.0-2+deb11u1 | vulnerable | |
| bookworm | 1.0.0-1+deb12u1 | vulnerable | |
| trixie | 1.4.0-1+deb13u1 | vulnerable | |
| forky, sid | 1.5.0-1 | vulnerable |
The information below is based on the following data on fixed versions.
| Package | Type | Release | Fixed Version | Urgency | Origin | Debian Bugs |
|---|---|---|---|---|---|---|
| log4cxx | source | (unstable) | (unfixed) |
https://github.com/apache/logging-log4cxx/pull/609
https://logging.apache.org/security.html#CVE-2026-40023
https://lists.apache.org/thread/y15cv3zblg3dfwr5vy6ddbnl4zyrzr8b