CVE-2026-34479 (GCVE-0-2026-34479)

Vulnerability from cvelistv5 – Published: 2026-04-10 15:41 – Updated: 2026-04-10 17:47
VLAI
Title
Apache Log4j 1 to Log4j 2 bridge: Silent log event loss in Log4j1XmlLayout due to unescaped XML 1.0 forbidden characters
Summary
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.
Severity
6.9 (Medium)
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
SSVC
Exploitation: none Automatable: yes Technical Impact: partial
CISA Coordinator (v2.0.3)
CWE
  • CWE-116 - Improper Encoding or Escaping of Output
Assigner
References
Impacted products
Vendor Product Version
Apache Software Foundation Apache Log4j 1 to Log4j 2 bridge Affected: 2.7 , < 2.25.4 (maven)
Affected: 3.0.0-alpha1 , ≤ 3.0.0-beta2 (maven)
    cpe:2.3:a:apache:log4j_1_2_api:*:*:*:*:*:*:*:*
 Create a notification for this product.
Credits
Ap4sh (Samy Medjahed) and Ethicxz (Eliott Laurie) (original reporters) jabaltarik1 (independently)
Show details on NVD website
To clipboard 

{
  "containers": {
    "adp": [
      {
        "providerMetadata": {
          "dateUpdated": "2026-04-10T16:18:18.699Z",
          "orgId": "af854a3a-2127-422b-91ae-364da2661108",
          "shortName": "CVE"
        },
        "references": [
          {
            "url": "http://www.openwall.com/lists/oss-security/2026/04/10/8"
          }
        ],
        "title": "CVE Program Container"
      },
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-34479",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-04-10T17:45:24.466114Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-04-10T17:47:34.402Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "collectionURL": "https://repo.maven.apache.org/maven2",
          "cpes": [
            "cpe:2.3:a:apache:log4j_1_2_api:*:*:*:*:*:*:*:*"
          ],
          "defaultStatus": "unaffected",
          "packageName": "org.apache.logging.log4j:log4j-1.2-api",
          "packageURL": "pkg:maven/org.apache.logging.log4j/log4j-1.2-api",
          "product": "Apache Log4j 1 to Log4j 2 bridge",
          "vendor": "Apache Software Foundation",
          "versions": [
            {
              "lessThan": "2.25.4",
              "status": "affected",
              "version": "2.7",
              "versionType": "maven"
            },
            {
              "lessThanOrEqual": "3.0.0-beta2",
              "status": "affected",
              "version": "3.0.0-alpha1",
              "versionType": "maven"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "finder",
          "value": "Ap4sh (Samy Medjahed) and Ethicxz (Eliott Laurie) (original reporters)"
        },
        {
          "lang": "en",
          "type": "finder",
          "value": "jabaltarik1 (independently)"
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "supportingMedia": [
            {
              "base64": false,
              "type": "text/html",
              "value": "\u003cp\u003eThe \u003ccode\u003eLog4j1XmlLayout\u003c/code\u003e 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.\u003c/p\u003e\u003cp\u003eTwo groups of users are affected:\u003c/p\u003e\u003cul\u003e\u003cli\u003eThose using \u003ccode\u003eLog4j1XmlLayout\u003c/code\u003e directly in a Log4j Core 2 configuration file.\u003c/li\u003e\u003cli\u003eThose using the Log4j 1 configuration compatibility layer with \u003ccode\u003eorg.apache.log4j.xml.XMLLayout\u003c/code\u003e specified as the layout class.\u003c/li\u003e\u003c/ul\u003e\u003cp\u003eUsers are advised to upgrade to Apache Log4j 1-to-Log4j 2 bridge version 2.25.4, which corrects this issue.\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eNote:\u003c/strong\u003e The Apache Log4j 1-to-Log4j 2 bridge is deprecated and will not be present in Log4j 3. Users are encouraged to consult the \u003ca target=\"_blank\" rel=\"nofollow\" href=\"https://logging.apache.org/log4j/2.x/migrate-from-log4j1.html\"\u003eLog4j 1 to Log4j 2 migration guide\u003c/a\u003e, and specifically the section on eliminating reliance on the bridge.\u003c/p\u003e"
            }
          ],
          "value": "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": [
        {
          "cvssV4_0": {
            "Automatable": "NOT_DEFINED",
            "Recovery": "NOT_DEFINED",
            "Safety": "NOT_DEFINED",
            "attackComplexity": "LOW",
            "attackRequirements": "NONE",
            "attackVector": "NETWORK",
            "baseScore": 6.9,
            "baseSeverity": "MEDIUM",
            "privilegesRequired": "NONE",
            "providerUrgency": "NOT_DEFINED",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "LOW",
            "userInteraction": "NONE",
            "valueDensity": "NOT_DEFINED",
            "vectorString": "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",
            "version": "4.0",
            "vulnAvailabilityImpact": "NONE",
            "vulnConfidentialityImpact": "NONE",
            "vulnIntegrityImpact": "NONE",
            "vulnerabilityResponseEffort": "NOT_DEFINED"
          },
          "format": "CVSS",
          "scenarios": [
            {
              "lang": "en",
              "value": "GENERAL"
            }
          ]
        },
        {
          "other": {
            "content": {
              "text": "moderate"
            },
            "type": "Textual description of severity"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-116",
              "description": "CWE-116 Improper Encoding or Escaping of Output",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-04-10T15:41:07.888Z",
        "orgId": "f0158376-9dc2-43b6-827c-5f631a4d8d09",
        "shortName": "apache"
      },
      "references": [
        {
          "tags": [
            "patch"
          ],
          "url": "https://github.com/apache/logging-log4j2/pull/4078"
        },
        {
          "tags": [
            "vendor-advisory"
          ],
          "url": "https://logging.apache.org/security.html#CVE-2026-34479"
        },
        {
          "tags": [
            "vendor-advisory"
          ],
          "url": "https://logging.apache.org/cyclonedx/vdr.xml"
        },
        {
          "tags": [
            "related"
          ],
          "url": "https://logging.apache.org/log4j/2.x/migrate-from-log4j1.html"
        },
        {
          "tags": [
            "vendor-advisory"
          ],
          "url": "https://lists.apache.org/thread/gd0hp6mj17rn3kj279vgy4p7kd4zz5on"
        }
      ],
      "source": {
        "discovery": "EXTERNAL"
      },
      "timeline": [
        {
          "lang": "en",
          "time": "2026-02-16T17:11:00.000Z",
          "value": "Vulnerability reported by Ap4sh and ethicxz"
        },
        {
          "lang": "en",
          "time": "2026-03-15T05:39:00.000Z",
          "value": "Independent report received from jabaltarik1"
        },
        {
          "lang": "en",
          "time": "2026-03-24T18:56:00.000Z",
          "value": "Fix shared publicly by Piotr P. Karwasz as pull request #4078"
        },
        {
          "lang": "en",
          "time": "2026-03-25T09:46:00.000Z",
          "value": "Fix verified by reporter"
        },
        {
          "lang": "en",
          "time": "2026-03-28T11:19:00.000Z",
          "value": "Log4j 2.25.4 released"
        }
      ],
      "title": "Apache Log4j 1 to Log4j 2 bridge: Silent log event loss in Log4j1XmlLayout due to unescaped XML 1.0 forbidden characters",
      "x_generator": {
        "engine": "Vulnogram 0.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "f0158376-9dc2-43b6-827c-5f631a4d8d09",
    "assignerShortName": "apache",
    "cveId": "CVE-2026-34479",
    "datePublished": "2026-04-10T15:41:07.888Z",
    "dateReserved": "2026-03-28T14:06:31.965Z",
    "dateUpdated": "2026-04-10T17:47:34.402Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-34479",
      "date": "2026-07-20",
      "epss": "0.00535",
      "percentile": "0.41606"
    },
    "microsoft_vex": {
      "current_release_date": "2026-04-30T01:40:38.000Z",
      "cve": "CVE-2026-34479",
      "id": "msrc_CVE-2026-34479",
      "initial_release_date": "2026-04-02T00:00:00.000Z",
      "product_status:known_not_affected": "1",
      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "Apache Log4j 1 to Log4j 2 bridge: Silent log event loss in Log4j1XmlLayout due to unescaped XML 1.0 forbidden characters",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-34479.json",
      "version": "3"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-34479\",\"sourceIdentifier\":\"security@apache.org\",\"published\":\"2026-04-10T16:16:31.270\",\"lastModified\":\"2026-06-17T10:39:06.947\",\"vulnStatus\":\"Analyzed\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"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.\"}],\"affected\":[{\"source\":\"security@apache.org\",\"affectedData\":[{\"vendor\":\"Apache Software Foundation\",\"product\":\"Apache Log4j 1 to Log4j 2 bridge\",\"defaultStatus\":\"unaffected\",\"collectionURL\":\"https://repo.maven.apache.org/maven2\",\"packageName\":\"org.apache.logging.log4j:log4j-1.2-api\",\"cpes\":[\"cpe:2.3:a:apache:log4j_1_2_api:*:*:*:*:*:*:*:*\"],\"packageURL\":\"pkg:maven/org.apache.logging.log4j/log4j-1.2-api\",\"versions\":[{\"version\":\"2.7\",\"lessThan\":\"2.25.4\",\"versionType\":\"maven\",\"status\":\"affected\"},{\"version\":\"3.0.0-alpha1\",\"lessThanOrEqual\":\"3.0.0-beta2\",\"versionType\":\"maven\",\"status\":\"affected\"}]}]}],\"metrics\":{\"cvssMetricV40\":[{\"source\":\"security@apache.org\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"4.0\",\"vectorString\":\"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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X\",\"baseScore\":6.9,\"baseSeverity\":\"MEDIUM\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"attackRequirements\":\"NONE\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"vulnConfidentialityImpact\":\"NONE\",\"vulnIntegrityImpact\":\"NONE\",\"vulnAvailabilityImpact\":\"NONE\",\"subConfidentialityImpact\":\"NONE\",\"subIntegrityImpact\":\"LOW\",\"subAvailabilityImpact\":\"NONE\",\"exploitMaturity\":\"NOT_DEFINED\",\"confidentialityRequirement\":\"NOT_DEFINED\",\"integrityRequirement\":\"NOT_DEFINED\",\"availabilityRequirement\":\"NOT_DEFINED\",\"modifiedAttackVector\":\"NOT_DEFINED\",\"modifiedAttackComplexity\":\"NOT_DEFINED\",\"modifiedAttackRequirements\":\"NOT_DEFINED\",\"modifiedPrivilegesRequired\":\"NOT_DEFINED\",\"modifiedUserInteraction\":\"NOT_DEFINED\",\"modifiedVulnConfidentialityImpact\":\"NOT_DEFINED\",\"modifiedVulnIntegrityImpact\":\"NOT_DEFINED\",\"modifiedVulnAvailabilityImpact\":\"NOT_DEFINED\",\"modifiedSubConfidentialityImpact\":\"NOT_DEFINED\",\"modifiedSubIntegrityImpact\":\"NOT_DEFINED\",\"modifiedSubAvailabilityImpact\":\"NOT_DEFINED\",\"Safety\":\"NOT_DEFINED\",\"Automatable\":\"NOT_DEFINED\",\"Recovery\":\"NOT_DEFINED\",\"valueDensity\":\"NOT_DEFINED\",\"vulnerabilityResponseEffort\":\"NOT_DEFINED\",\"providerUrgency\":\"NOT_DEFINED\"}}],\"cvssMetricV31\":[{\"source\":\"nvd@nist.gov\",\"type\":\"Primary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N\",\"baseScore\":7.5,\"baseSeverity\":\"HIGH\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"NONE\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"NONE\"},\"exploitabilityScore\":3.9,\"impactScore\":3.6}],\"ssvcV203\":[{\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"ssvcData\":{\"timestamp\":\"2026-04-10T17:45:24.466114Z\",\"id\":\"CVE-2026-34479\",\"options\":[{\"exploitation\":\"none\"},{\"automatable\":\"yes\"},{\"technicalImpact\":\"partial\"}],\"role\":\"CISA Coordinator\",\"version\":\"2.0.3\"}}]},\"weaknesses\":[{\"source\":\"security@apache.org\",\"type\":\"Secondary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-116\"}]}],\"configurations\":[{\"nodes\":[{\"operator\":\"OR\",\"negate\":false,\"cpeMatch\":[{\"vulnerable\":true,\"criteria\":\"cpe:2.3:a:apache:log4j:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"2.7\",\"versionEndExcluding\":\"2.25.4\",\"matchCriteriaId\":\"4D7C1729-01D6-4981-B3FB-3A877083AE28\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:a:apache:log4j:3.0.0:alpha1:*:*:*:*:*:*\",\"matchCriteriaId\":\"5EE518C3-2F43-40FF-B754-C340B7003FC7\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:a:apache:log4j:3.0.0:alpha1_rc1:*:*:*:*:*:*\",\"matchCriteriaId\":\"6D2A01C1-D56C-4198-8ADB-11739F791E2B\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:a:apache:log4j:3.0.0:alpha1_rc2:*:*:*:*:*:*\",\"matchCriteriaId\":\"D6F8BD61-DD30-4D64-842C-850E5B117036\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:a:apache:log4j:3.0.0:beta1:*:*:*:*:*:*\",\"matchCriteriaId\":\"ED00C38D-27EA-489C-9A2B-3594ACA8A3C5\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:a:apache:log4j:3.0.0:beta2:*:*:*:*:*:*\",\"matchCriteriaId\":\"8794D719-1D90-4378-B48B-698EA40FBFB2\"}]}]}],\"references\":[{\"url\":\"https://github.com/apache/logging-log4j2/pull/4078\",\"source\":\"security@apache.org\",\"tags\":[\"Exploit\",\"Issue Tracking\",\"Patch\"]},{\"url\":\"https://lists.apache.org/thread/gd0hp6mj17rn3kj279vgy4p7kd4zz5on\",\"source\":\"security@apache.org\",\"tags\":[\"Mailing List\"]},{\"url\":\"https://logging.apache.org/cyclonedx/vdr.xml\",\"source\":\"security@apache.org\",\"tags\":[\"Vendor Advisory\"]},{\"url\":\"https://logging.apache.org/log4j/2.x/migrate-from-log4j1.html\",\"source\":\"security@apache.org\",\"tags\":[\"Mitigation\"]},{\"url\":\"https://logging.apache.org/security.html#CVE-2026-34479\",\"source\":\"security@apache.org\",\"tags\":[\"Vendor Advisory\"]},{\"url\":\"http://www.openwall.com/lists/oss-security/2026/04/10/8\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\",\"tags\":[\"Mailing List\"]}]}}",
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-07-20T10:29:40+00:00",
      "cve": "CVE-2026-34479",
      "id": "CVE-2026-34479",
      "initial_release_date": "2026-04-10T15:41:07.888000+00:00",
      "product_status:fixed": "2",
      "product_status:known_affected": "16",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "org.apache.logging.log4j/log4j-1.2-api: Apache Log4j 1-to-Log4j 2 bridge: Log processing denial of service due to improper XML escaping",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-34479.json",
      "version": "3"
    },
    "vulnrichment": {
      "containers": "{\"adp\": [{\"title\": \"CVE Program Container\", \"references\": [{\"url\": \"http://www.openwall.com/lists/oss-security/2026/04/10/8\"}], \"providerMetadata\": {\"orgId\": \"af854a3a-2127-422b-91ae-364da2661108\", \"shortName\": \"CVE\", \"dateUpdated\": \"2026-04-10T16:18:18.699Z\"}}, {\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2026-34479\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"yes\"}, {\"Technical Impact\": \"partial\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-04-10T17:45:24.466114Z\"}}}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-04-10T17:47:19.925Z\"}}], \"cna\": {\"title\": \"Apache Log4j 1 to Log4j 2 bridge: Silent log event loss in Log4j1XmlLayout due to unescaped XML 1.0 forbidden characters\", \"source\": {\"discovery\": \"EXTERNAL\"}, \"credits\": [{\"lang\": \"en\", \"type\": \"finder\", \"value\": \"Ap4sh (Samy Medjahed) and Ethicxz (Eliott Laurie) (original reporters)\"}, {\"lang\": \"en\", \"type\": \"finder\", \"value\": \"jabaltarik1 (independently)\"}], \"metrics\": [{\"format\": \"CVSS\", \"cvssV4_0\": {\"Safety\": \"NOT_DEFINED\", \"version\": \"4.0\", \"Recovery\": \"NOT_DEFINED\", \"baseScore\": 6.9, \"Automatable\": \"NOT_DEFINED\", \"attackVector\": \"NETWORK\", \"baseSeverity\": \"MEDIUM\", \"valueDensity\": \"NOT_DEFINED\", \"vectorString\": \"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\", \"providerUrgency\": \"NOT_DEFINED\", \"userInteraction\": \"NONE\", \"attackComplexity\": \"LOW\", \"attackRequirements\": \"NONE\", \"privilegesRequired\": \"NONE\", \"subIntegrityImpact\": \"LOW\", \"vulnIntegrityImpact\": \"NONE\", \"subAvailabilityImpact\": \"NONE\", \"vulnAvailabilityImpact\": \"NONE\", \"subConfidentialityImpact\": \"NONE\", \"vulnConfidentialityImpact\": \"NONE\", \"vulnerabilityResponseEffort\": \"NOT_DEFINED\"}, \"scenarios\": [{\"lang\": \"en\", \"value\": \"GENERAL\"}]}, {\"other\": {\"type\": \"Textual description of severity\", \"content\": {\"text\": \"moderate\"}}}], \"affected\": [{\"cpes\": [\"cpe:2.3:a:apache:log4j_1_2_api:*:*:*:*:*:*:*:*\"], \"vendor\": \"Apache Software Foundation\", \"product\": \"Apache Log4j 1 to Log4j 2 bridge\", \"versions\": [{\"status\": \"affected\", \"version\": \"2.7\", \"lessThan\": \"2.25.4\", \"versionType\": \"maven\"}, {\"status\": \"affected\", \"version\": \"3.0.0-alpha1\", \"versionType\": \"maven\", \"lessThanOrEqual\": \"3.0.0-beta2\"}], \"packageURL\": \"pkg:maven/org.apache.logging.log4j/log4j-1.2-api\", \"packageName\": \"org.apache.logging.log4j:log4j-1.2-api\", \"collectionURL\": \"https://repo.maven.apache.org/maven2\", \"defaultStatus\": \"unaffected\"}], \"timeline\": [{\"lang\": \"en\", \"time\": \"2026-02-16T17:11:00.000Z\", \"value\": \"Vulnerability reported by Ap4sh and ethicxz\"}, {\"lang\": \"en\", \"time\": \"2026-03-15T05:39:00.000Z\", \"value\": \"Independent report received from jabaltarik1\"}, {\"lang\": \"en\", \"time\": \"2026-03-24T18:56:00.000Z\", \"value\": \"Fix shared publicly by Piotr P. Karwasz as pull request #4078\"}, {\"lang\": \"en\", \"time\": \"2026-03-25T09:46:00.000Z\", \"value\": \"Fix verified by reporter\"}, {\"lang\": \"en\", \"time\": \"2026-03-28T11:19:00.000Z\", \"value\": \"Log4j 2.25.4 released\"}], \"references\": [{\"url\": \"https://github.com/apache/logging-log4j2/pull/4078\", \"tags\": [\"patch\"]}, {\"url\": \"https://logging.apache.org/security.html#CVE-2026-34479\", \"tags\": [\"vendor-advisory\"]}, {\"url\": \"https://logging.apache.org/cyclonedx/vdr.xml\", \"tags\": [\"vendor-advisory\"]}, {\"url\": \"https://logging.apache.org/log4j/2.x/migrate-from-log4j1.html\", \"tags\": [\"related\"]}, {\"url\": \"https://lists.apache.org/thread/gd0hp6mj17rn3kj279vgy4p7kd4zz5on\", \"tags\": [\"vendor-advisory\"]}], \"x_generator\": {\"engine\": \"Vulnogram 0.2.0\"}, \"descriptions\": [{\"lang\": \"en\", \"value\": \"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.\", \"supportingMedia\": [{\"type\": \"text/html\", \"value\": \"\u003cp\u003eThe \u003ccode\u003eLog4j1XmlLayout\u003c/code\u003e 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.\u003c/p\u003e\u003cp\u003eTwo groups of users are affected:\u003c/p\u003e\u003cul\u003e\u003cli\u003eThose using \u003ccode\u003eLog4j1XmlLayout\u003c/code\u003e directly in a Log4j Core 2 configuration file.\u003c/li\u003e\u003cli\u003eThose using the Log4j 1 configuration compatibility layer with \u003ccode\u003eorg.apache.log4j.xml.XMLLayout\u003c/code\u003e specified as the layout class.\u003c/li\u003e\u003c/ul\u003e\u003cp\u003eUsers are advised to upgrade to Apache Log4j 1-to-Log4j 2 bridge version 2.25.4, which corrects this issue.\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eNote:\u003c/strong\u003e The Apache Log4j 1-to-Log4j 2 bridge is deprecated and will not be present in Log4j 3. Users are encouraged to consult the \u003ca target=\\\"_blank\\\" rel=\\\"nofollow\\\" href=\\\"https://logging.apache.org/log4j/2.x/migrate-from-log4j1.html\\\"\u003eLog4j 1 to Log4j 2 migration guide\u003c/a\u003e, and specifically the section on eliminating reliance on the bridge.\u003c/p\u003e\", \"base64\": false}]}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-116\", \"description\": \"CWE-116 Improper Encoding or Escaping of Output\"}]}], \"providerMetadata\": {\"orgId\": \"f0158376-9dc2-43b6-827c-5f631a4d8d09\", \"shortName\": \"apache\", \"dateUpdated\": \"2026-04-10T15:41:07.888Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-34479\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-04-10T17:47:34.402Z\", \"dateReserved\": \"2026-03-28T14:06:31.965Z\", \"assignerOrgId\": \"f0158376-9dc2-43b6-827c-5f631a4d8d09\", \"datePublished\": \"2026-04-10T15:41:07.888Z\", \"assignerShortName\": \"apache\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.