{
  "affected": [
    {
      "ranges": [
        {
          "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"
            ]
          },
          "events": [
            {
              "introduced": "29cfc80dcddd468c1c5d4ef2c7c4435f90792628"
            },
            {
              "fixed": "0628e53b25a33e496b509c40a39f2d7c64f2aa6c"
            },
            {
              "introduced": "e84827220de69f39112d5f518279038c152b186f"
            }
          ],
          "repo": "https://github.com/apache/logging-log4j2",
          "type": "GIT"
        }
      ],
      "versions": [
        "3.0.0-alpha1",
        "3.0.0-beta1",
        "3.0.0-beta2"
      ]
    }
  ],
  "database_specific": {
    "cna_assigner": "apache",
    "cwe_ids": [
      "CWE-116"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/34xxx/CVE-2026-34479.json"
  },
  "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.",
  "id": "CVE-2026-34479",
  "modified": "2026-07-08T05:36:34.956192361Z",
  "published": "2026-04-10T15:41:07.888Z",
  "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"
    }
  ],
  "schema_version": "1.7.5",
  "severity": [
    {
      "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",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Apache Log4j 1 to Log4j 2 bridge: Silent log event loss in Log4j1XmlLayout due to unescaped XML 1.0 forbidden characters"
}