CVE-2026-34479
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
Versions sourced from the GitHub Security Advisory.
| Package | Affected versions | Patched versions |
|---|---|---|
org.apache.logging.log4j:log4j-1.2-apiMaven | >= 2.7, < 2.25.4 | 2.25.4 |
org.apache.logging.log4j:log4j-1.2-apiMaven | >= 3.0.0-beta1, <= 3.0.0-beta2 | — |
Affected products
7cpe:2.3:a:apache:log4j:*:*:*:*:*:*:*:*+ 5 more
- cpe:2.3:a:apache:log4j:*:*:*:*:*:*:*:*range: >=2.7,<2.25.4
- cpe:2.3:a:apache:log4j:3.0.0:alpha1:*:*:*:*:*:*
- cpe:2.3:a:apache:log4j:3.0.0:alpha1_rc1:*:*:*:*:*:*
- cpe:2.3:a:apache:log4j:3.0.0:alpha1_rc2:*:*:*:*:*:*
- cpe:2.3:a:apache:log4j:3.0.0:beta1:*:*:*:*:*:*
- cpe:2.3:a:apache:log4j:3.0.0:beta2:*:*:*:*:*:*
Patches
0No patches discovered yet.
Vulnerability mechanics
AI mechanics synthesis has not run for this CVE yet.
References
8- github.com/apache/logging-log4j2/pull/4078nvdExploitIssue TrackingPatchWEB
- github.com/advisories/GHSA-h383-gmxw-35v2ghsaADVISORY
- logging.apache.org/cyclonedx/vdr.xmlnvdVendor AdvisoryWEB
- logging.apache.org/security.htmlnvdVendor AdvisoryWEB
- nvd.nist.gov/vuln/detail/CVE-2026-34479ghsaADVISORY
- www.openwall.com/lists/oss-security/2026/04/10/8nvdMailing ListWEB
- lists.apache.org/thread/gd0hp6mj17rn3kj279vgy4p7kd4zz5onnvdMailing ListWEB
- logging.apache.org/log4j/2.x/migrate-from-log4j1.htmlnvdMitigationWEB
News mentions
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