{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-34479", "assignerOrgId": "f0158376-9dc2-43b6-827c-5f631a4d8d09", "state": "PUBLISHED", "assignerShortName": "apache", "dateReserved": "2026-03-28T14:06:31.965Z", "datePublished": "2026-04-10T15:41:07.888Z", "dateUpdated": "2026-04-10T16:18:18.699Z"}, "containers": {"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": "<p>The <code>Log4j1XmlLayout</code> 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.</p><p>Two groups of users are affected:</p><ul><li>Those using <code>Log4j1XmlLayout</code> directly in a Log4j Core 2 configuration file.</li><li>Those using the Log4j 1 configuration compatibility layer with <code>org.apache.log4j.xml.XMLLayout</code> specified as the layout class.</li></ul><p>Users are advised to upgrade to Apache Log4j 1-to-Log4j 2 bridge version 2.25.4, which corrects this issue.</p><p><strong>Note:</strong> The Apache Log4j 1-to-Log4j 2 bridge is deprecated and will not be present in Log4j 3. Users are encouraged to consult the <a target=\"_blank\" rel=\"nofollow\" href=\"https://logging.apache.org/log4j/2.x/migrate-from-log4j1.html\">Log4j 1 to Log4j 2 migration guide</a>, and specifically the section on eliminating reliance on the bridge.</p>"}], "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": {"orgId": "f0158376-9dc2-43b6-827c-5f631a4d8d09", "shortName": "apache", "dateUpdated": "2026-04-10T15:41:07.888Z"}, "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"}}, "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"}}]}}

{}

{"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."}], "id": "CVE-2026-34479", "lastModified": "2026-04-10T17:17:02.403", "metrics": {"cvssMetricV40": [{"cvssData": {"Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "Safety": "NOT_DEFINED", "attackComplexity": "LOW", "attackRequirements": "NONE", "attackVector": "NETWORK", "availabilityRequirement": "NOT_DEFINED", "baseScore": 6.9, "baseSeverity": "MEDIUM", "confidentialityRequirement": "NOT_DEFINED", "exploitMaturity": "NOT_DEFINED", "integrityRequirement": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "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/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", "version": "4.0", "vulnAvailabilityImpact": "NONE", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "NONE", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "source": "security@apache.org", "type": "Secondary"}]}, "published": "2026-04-10T16:16:31.270", "references": [{"source": "security@apache.org", "url": "https://github.com/apache/logging-log4j2/pull/4078"}, {"source": "security@apache.org", "url": "https://lists.apache.org/thread/gd0hp6mj17rn3kj279vgy4p7kd4zz5on"}, {"source": "security@apache.org", "url": "https://logging.apache.org/cyclonedx/vdr.xml"}, {"source": "security@apache.org", "url": "https://logging.apache.org/log4j/2.x/migrate-from-log4j1.html"}, {"source": "security@apache.org", "url": "https://logging.apache.org/security.html#CVE-2026-34479"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "url": "http://www.openwall.com/lists/oss-security/2026/04/10/8"}], "sourceIdentifier": "security@apache.org", "vulnStatus": "Received", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-116"}], "source": "security@apache.org", "type": "Secondary"}]}

{}

{}