{
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    {
      "id": "GHSA-h383-gmxw-35v2",
      "source": "ghsa",
      "title": "Apache Log4j 1 to Log4j 2 bridge: silent log event loss in Log4j1XmlLayout due to unescaped XML 1.0 forbidden characters",
      "url": "https://github.com/advisories/GHSA-h383-gmxw-35v2"
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  "cve": "CVE-2026-34479",
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            "Upgrade the Apache Log4j 1-to-Log4j 2 bridge to version 2.25.4 or later.",
            "If the bridge is no longer needed, remove it from the application to eliminate the vulnerability.",
            "Disable Log4j1XmlLayout or the XMLLayout class when they are not required.",
            "Verify that downstream log processing systems correctly handle escaped characters and monitor for missing events.",
            "Follow the Log4j 1 to Log4j 2 migration guide to phase out the bridge entirely."
          ],
          "summary": {
            "action": "Patch Upgrade",
            "impact": "Silent log event loss via malformed XML"
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    "cpes": [],
    "created": "2026-04-10T15:41:07.888000+00:00",
    "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.\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.",
    "metrics": {
      "cvssV2_0": {},
      "cvssV3_0": {},
      "cvssV3_1": {},
      "cvssV4_0": {},
      "kev": {},
      "ssvc": {
        "options": {
          "Automatable": "yes",
          "Exploitation": "none",
          "Technical Impact": "partial"
        },
        "version": "2.0.3"
      }
    },
    "references": [],
    "title": "Apache Log4j 1 to Log4j 2 bridge: Silent log event loss in Log4j1XmlLayout due to unescaped XML 1.0 forbidden characters",
    "updated": "2026-04-10T17:47:19.925000+00:00",
    "vendors": [],
    "vulnrichment_repo_path": "2026/34xxx/CVE-2026-34479.json",
    "weaknesses": []
  }
}