| Name | CVE-2026-34480 |
| Description | Apache Log4j Core's XmlLayout https://logging.apache.org/log4j/2.x/manual/layouts.html#XmlLayout , in versions up to and including 2.25.3, fails to sanitize characters forbidden by the XML 1.0 specification https://www.w3.org/TR/xml/#charsets producing invalid XML output whenever a log message or MDC value contains such characters. The impact depends on the StAX implementation in use: * JRE built-in StAX: Forbidden characters are silently written to the output, producing malformed XML. Conforming parsers must reject such documents with a fatal error, which may cause downstream log-processing systems to drop the affected records. * Alternative StAX implementations (e.g., Woodstox https://github.com/FasterXML/woodstox , a transitive dependency of the Jackson XML Dataformat module): An exception is thrown during the logging call, and the log event is never delivered to its intended appender, only to Log4j's internal status logger. Users are advised to upgrade to Apache Log4j Core 2.25.4, which corrects this issue by sanitizing forbidden characters before XML output. |
| 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) |
| Debian Bugs | 1133847, 1136032 |
The table below lists information on source packages.
| Source Package | Release | Version | Status |
|---|---|---|---|
| apache-log4j1.2 (PTS) | bullseye | 1.2.17-10+deb11u1 | vulnerable |
| forky, sid, bookworm, trixie | 1.2.17-11 | vulnerable | |
| apache-log4j2 (PTS) | bullseye | 2.17.1-1~deb11u1 | vulnerable |
| bullseye (security) | 2.17.1-1~deb11u2 | vulnerable | |
| forky, sid, bookworm, trixie | 2.19.0-2 | vulnerable |
The information below is based on the following data on fixed versions.
| Package | Type | Release | Fixed Version | Urgency | Origin | Debian Bugs |
|---|---|---|---|---|---|---|
| apache-log4j1.2 | source | (unstable) | (unfixed) | 1136032 | ||
| apache-log4j2 | source | (unstable) | (unfixed) | 1133847 |
[trixie] - apache-log4j2 <no-dsa> (Minor issue)
[bookworm] - apache-log4j2 <no-dsa> (Minor issue)
[bullseye] - apache-log4j2 <postponed> (Minor issue, can be fixed with next upload)
[trixie] - apache-log4j1.2 <no-dsa> (Minor issue)
[bookworm] - apache-log4j1.2 <no-dsa> (Minor issue)
[bullseye] - apache-log4j1.2 <postponed> (Minor issue, can be fixed with next upload)
https://lists.apache.org/thread/5x0hcnng0chhghp6jgjdp3qmbbhfjzhb
https://logging.apache.org/security.html#CVE-2026-34480
https://github.com/apache/logging-log4j2/pull/4077
Fixed by: https://github.com/apache/logging-log4j2/commit/4f5014229825d8be977662e0743205bb8a67f989 (rel/2.25.4)