FKIE_CVE-2026-34478

Vulnerability from fkie_nvd - Published: 2026-04-10 16:16 - Updated: 2026-10-26 22:10
Severity
7.5 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Summary
Apache Log4j Core's Rfc5424Layout https://logging.apache.org/log4j/2.x/manual/layouts.html#RFC5424Layout , in versions 2.21.0 through 2.25.3, is vulnerable to log injection via CRLF sequences due to undocumented renames of security-relevant configuration attributes. Two distinct issues affect users of stream-based syslog services who configure Rfc5424Layout directly: * The newLineEscape attribute was silently renamed, causing newline escaping to stop working for users of TCP framing (RFC 6587), exposing them to CRLF injection in log output. * The useTlsMessageFormat attribute was silently renamed, causing users of TLS framing (RFC 5425) to be silently downgraded to unframed TCP (RFC 6587), without newline escaping. Users of the SyslogAppender are not affected, as its configuration attributes were not modified. Users are advised to upgrade to Apache Log4j Core 2.25.4, which corrects this issue.
References
security@apache.orghttps://github.com/apache/logging-log4j2/pull/4074Issue Tracking, Patch
security@apache.orghttps://lists.apache.org/thread/3k1clr2l6vkdnl4cbhjrnt1nyjvb5gwtMailing List, Vendor Advisory
security@apache.orghttps://logging.apache.org/cyclonedx/vdr.xmlProduct
security@apache.orghttps://logging.apache.org/log4j/2.x/manual/layouts.html#RFC5424LayoutTechnical Description
security@apache.orghttps://logging.apache.org/security.html#CVE-2026-34478Vendor Advisory
af854a3a-2127-422b-91ae-364da2661108http://www.openwall.com/lists/oss-security/2026/04/10/7Mailing List, Third Party Advisory
Impacted products
Vendor Product Version
apache log4j *
apache log4j 3.0.0
apache log4j 3.0.0
apache log4j 3.0.0
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "collectionURL": "https://repo.maven.apache.org/maven2",
          "cpes": [
            "cpe:2.3:a:apache:log4j:*:*:*:*:*:*:*:*"
          ],
          "defaultStatus": "unaffected",
          "packageName": "org.apache.logging.log4j:log4j-core",
          "packageURL": "pkg:maven/org.apache.logging.log4j/log4j-core",
          "product": "Apache Log4j Core",
          "vendor": "Apache Software Foundation",
          "versions": [
            {
              "lessThan": "2.25.4",
              "status": "affected",
              "version": "2.21.0",
              "versionType": "maven"
            },
            {
              "lessThanOrEqual": "3.0.0-beta3",
              "status": "affected",
              "version": "3.0.0-beta1",
              "versionType": "maven"
            }
          ]
        }
      ],
      "source": "security@apache.org"
    }
  ],
  "configurations": [
    {
      "nodes": [
        {
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:apache:log4j:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "4928759D-3A0D-4BC2-85BC-2CFAF137B4A0",
              "versionEndExcluding": "2.25.4",
              "versionStartIncluding": "2.21.0",
              "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",
              "vulnerable": true
            },
            {
              "criteria": "cpe:2.3:a:apache:log4j:3.0.0:beta3:*:*:*:*:*:*",
              "matchCriteriaId": "74C9FCBD-ECAD-4C29-B97A-2B9D97C0FC1F",
              "vulnerable": true
            }
          ],
          "negate": false,
          "operator": "OR"
        }
      ]
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Apache Log4j Core\u0027s  Rfc5424Layout https://logging.apache.org/log4j/2.x/manual/layouts.html#RFC5424Layout , in versions 2.21.0 through 2.25.3, is vulnerable to log injection via CRLF sequences due to undocumented renames of security-relevant configuration attributes.\n\nTwo distinct issues affect users of stream-based syslog services who configure Rfc5424Layout directly:\n\n  *  The newLineEscape attribute was silently renamed, causing newline escaping to stop working for users of TCP framing (RFC 6587), exposing them to CRLF injection in log output.\n  *  The useTlsMessageFormat attribute was silently renamed, causing users of TLS framing (RFC 5425) to be silently downgraded to unframed TCP (RFC 6587), without newline escaping.\n\n\nUsers of the SyslogAppender are not affected, as its configuration attributes were not modified.\n\nUsers are advised to upgrade to Apache Log4j Core 2.25.4, which corrects this issue."
    },
    {
      "lang": "es",
      "value": "El Rfc5424Layout de Apache Log4j Core https://logging.apache.org/log4j/2.x/manual/layouts.html#RFC5424Layout , en las versiones 2.21.0 a 2.25.3, es vulnerable a la inyecci\u00f3n de registros a trav\u00e9s de secuencias CRLF debido a cambios de nombre no documentados de atributos de configuraci\u00f3n relevantes para la seguridad.\n\nDos problemas distintos afectan a los usuarios de servicios syslog basados en flujo que configuran Rfc5424Layout directamente:\n\n  *  El atributo newLineEscape fue renombrado silenciosamente, lo que provoc\u00f3 que el escape de nueva l\u00ednea dejara de funcionar para los usuarios de tramas TCP (RFC 6587), exponi\u00e9ndolos a la inyecci\u00f3n de CRLF en la salida de registros.\n  *  El atributo useTlsMessageFormat fue renombrado silenciosamente, lo que provoc\u00f3 que los usuarios de tramas TLS (RFC 5425) fueran degradados silenciosamente a TCP sin tramas (RFC 6587), sin escape de nueva l\u00ednea.\n\nLos usuarios del SyslogAppender no se ven afectados, ya que sus atributos de configuraci\u00f3n no fueron modificados.\n\nSe aconseja a los usuarios actualizar a Apache Log4j Core 2.25.4, que corrige este problema."
    }
  ],
  "id": "CVE-2026-34478",
  "lastModified": "2026-10-26T22:10:00.163",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "NONE",
          "baseScore": 7.5,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "NONE",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 3.6,
        "source": "nvd@nist.gov",
        "type": "Primary"
      }
    ],
    "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"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-34478",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-04-10T17:48:27.852992Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-04-10T16:16:31.070",
  "references": [
    {
      "source": "security@apache.org",
      "tags": [
        "Issue Tracking",
        "Patch"
      ],
      "url": "https://github.com/apache/logging-log4j2/pull/4074"
    },
    {
      "source": "security@apache.org",
      "tags": [
        "Mailing List",
        "Vendor Advisory"
      ],
      "url": "https://lists.apache.org/thread/3k1clr2l6vkdnl4cbhjrnt1nyjvb5gwt"
    },
    {
      "source": "security@apache.org",
      "tags": [
        "Product"
      ],
      "url": "https://logging.apache.org/cyclonedx/vdr.xml"
    },
    {
      "source": "security@apache.org",
      "tags": [
        "Technical Description"
      ],
      "url": "https://logging.apache.org/log4j/2.x/manual/layouts.html#RFC5424Layout"
    },
    {
      "source": "security@apache.org",
      "tags": [
        "Vendor Advisory"
      ],
      "url": "https://logging.apache.org/security.html#CVE-2026-34478"
    },
    {
      "source": "af854a3a-2127-422b-91ae-364da2661108",
      "tags": [
        "Mailing List",
        "Third Party Advisory"
      ],
      "url": "http://www.openwall.com/lists/oss-security/2026/04/10/7"
    }
  ],
  "sourceIdentifier": "security@apache.org",
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-117"
        },
        {
          "lang": "en",
          "value": "CWE-684"
        }
      ],
      "source": "security@apache.org",
      "type": "Secondary"
    }
  ]
}



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