GHSA-h383-gmxw-35v2
Apache Log4j 1 to Log4j 2 bridge: silent log event loss in Log4j1XmlLayout due to unescaped XML 1.0 forbidden characters
At a glance
- Published
- Updated
- CVE
- CVE-2026-34479
- CVSS_V4
- CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N
Description
The `Log4j1XmlLayout` from the Apache Log4j 1-to-Log4j 2 bridge fails to escape characters forbidden by the XML 1.0 standard, producing malformed XML output. Conforming XML parsers are required to reject documents containing such characters with a fatal error, which may cause downstream log processing systems to drop or fail to index affected records. Two groups of users are affected: * Those using `Log4j1XmlLayout` directly in a Log4j Core 2 configuration file. * Those using the Log4j 1 configuration compatibility layer with `org.apache.log4j.xml.XMLLayout` specified as the layout class. Users are advised to upgrade to Apache Log4j 1-to-Log4j 2 bridge version `2.25.4`, which corrects this issue. > [!NOTE] > The Apache Log4j 1-to-Log4j 2 bridge is deprecated and will not be present in Log4j 3. Users are encouraged to consult the > [Log4j 1 to Log4j 2 migration guide](https://logging.apache.org/log4j/2.x/migrate-from-log4j1.html), and specifically the section on eliminating reliance on the bridge.
Affected packages
| Package | Versions |
|---|---|
| Maven · org.apache.logging.log4j:log4j-core | introduced 2.7, fixed 2.25.4 |
| Maven · org.apache.logging.log4j:log4j-core | introduced 3.0.0-beta1, last affected 3.0.0-beta2 |
References
- https://nvd.nist.gov/vuln/detail/CVE-2026-34479 ADVISORY
- https://github.com/apache/logging-log4j2/pull/4078 WEB
- https://github.com/apache/logging-log4j2 PACKAGE
- https://lists.apache.org/thread/gd0hp6mj17rn3kj279vgy4p7kd4zz5on WEB
- https://logging.apache.org/cyclonedx/vdr.xml WEB
- https://logging.apache.org/log4j/2.x/migrate-from-log4j1.html WEB
- https://logging.apache.org/security.html#CVE-2026-34479 WEB
- http://www.openwall.com/lists/oss-security/2026/04/10/8 WEB
Sources
| Source | Licence |
|---|---|
| OSV.dev | CC-BY 4.0 — GitHub Advisory Database |