{"id":"CVE-2026-34479","summary":"Apache Log4j 1 to Log4j 2 bridge: Silent log event loss in Log4j1XmlLayout due to unescaped XML 1.0 forbidden characters","details":"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.\n\nTwo groups of users are affected:\n\n  *  Those using Log4j1XmlLayout directly in a Log4j Core 2 configuration file.\n  *  Those using the Log4j 1 configuration compatibility layer with org.apache.log4j.xml.XMLLayout specified as the layout class.\n\n\nUsers are advised to upgrade to Apache Log4j 1-to-Log4j 2 bridge version 2.25.4, which corrects this issue.\n\nNote: 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.","aliases":["GHSA-h383-gmxw-35v2"],"modified":"2026-07-08T08:12:50.259595358Z","published":"2026-04-10T15:41:07.888Z","related":["CGA-xv36-79hh-mj43","SUSE-SU-2026:1843-1","openSUSE-SU-2026:10544-1"],"database_specific":{"cna_assigner":"apache","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/34xxx/CVE-2026-34479.json","cwe_ids":["CWE-116"]},"references":[{"type":"WEB","url":"http://www.openwall.com/lists/oss-security/2026/04/10/8"},{"type":"WEB","url":"https://logging.apache.org/log4j/2.x/migrate-from-log4j1.html"},{"type":"WEB","url":"https://repo.maven.apache.org/maven2"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/34xxx/CVE-2026-34479.json"},{"type":"ADVISORY","url":"https://lists.apache.org/thread/gd0hp6mj17rn3kj279vgy4p7kd4zz5on"},{"type":"ADVISORY","url":"https://logging.apache.org/cyclonedx/vdr.xml"},{"type":"ADVISORY","url":"https://logging.apache.org/security.html#CVE-2026-34479"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-34479"},{"type":"FIX","url":"https://github.com/apache/logging-log4j2/pull/4078"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/apache/logging-log4j2","events":[{"introduced":"29cfc80dcddd468c1c5d4ef2c7c4435f90792628"},{"fixed":"0628e53b25a33e496b509c40a39f2d7c64f2aa6c"},{"introduced":"e84827220de69f39112d5f518279038c152b186f"}],"database_specific":{"cpe":["cpe:2.3:a:apache:log4j:*:*:*:*:*:*:*:*","cpe:2.3:a:apache:log4j:3.0.0:alpha1:*:*:*:*:*:*","cpe:2.3:a:apache:log4j:3.0.0:beta1:*:*:*:*:*:*","cpe:2.3:a:apache:log4j:3.0.0:beta2:*:*:*:*:*:*"],"extracted_events":[{"introduced":"2.7"},{"fixed":"2.25.4"},{"introduced":"3.0.0-alpha1"},{"last_affected":"3.0.0-alpha1"},{"introduced":"3.0.0-beta1"},{"last_affected":"3.0.0-beta1"},{"introduced":"3.0.0-beta2"},{"last_affected":"3.0.0-beta2"}],"source":["CPE_RANGE","CPE_STRING"]}}],"versions":["3.0.0-alpha1","3.0.0-beta1","3.0.0-beta2","rel/2.25.3","rel/2.25.2","rel/2.25.1","rel/2.25.0","rel/2.20.0","log4j-2.20.0-rc1","rel/2.19.0","log4j-2.19.0-rc2","log4j-2.19.0-rc1","rel/2.18.0","log4j-2.18.0-rc1","rel/2.17.2","log4j-2.17.2-rc1","rel/2.17.1","log4j-2.17.1-rc1","rel/2.17.0","log4j-2.17.0-rc1","rel/2.12.1","log4j-2.12.1-rc1","log4j-2.12.1","rel/2.16.0","log4j-2.16.0-rc1","log4j-2.15.1-rc1","rel/2.15.0","log4j-2.15.0-rc2","log4j-2.15.0-rc1","rel/2.14.1","log4j-2.14.1-rc1","rel/2.14.0","log4j-2.14.0-rc1","rel/2.13.3","log4j-2.13.3-rc1","log4j-2.13.3","rel/2.13.2","log4j-2.13.2-rc1","log4j-2.13.2","rel/2.13.1","log4j-2.13.1-rc2","log4j-2.13.1","log4j-2.13.1-rc1","rel/2.13.0","log4j-2.13.0-rc2","log4j-2.13.0-rc1","log4j-2.12.0-rc2","rel/2.12.0","log4j-2.12.0-rc1","log4j-2.12.0","rel/2.11.2","log4j-2.11.2-rc3","log4j-2.11.2","log4j-2.11.2-rc2","log4j-2.11.2-rc1","rel/2.11.1","log4j-2.11.1-rc1","log4j-2.11.1","rel/2.11.0","log4j-2.11.0-rc1","log4j-2.11.0","rel/2.10.0","log4j-2.10.0","log4j-2.10-rc1","log4j-2.9.1-rc1","rel/2.9.0","log4j-2.9.0","log4j-2.9-rc1","rel/2.8.1","log4j-2.8.1-rc1","log4j-2.8.1","rel/2.8","log4j-2.8-rc1","log4j-2.8","rel/2.7","log4j-2.7-rc2","log4j-2.7"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-34479.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V4","score":"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"}]}