CVE-2026-34478
Full vulnerability record from the local CVENow database.
Description
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.
Severity
MEDIUM
CVSS score
6.9
(v4.0)
Vulnerability status
Analyzed
Source identifier
Published
2026-04-10 16:16:31.070000
Last modified
2026-10-26 22:10:00.163000
View original CVE JSON
{
"id": "CVE-2026-34478",
"sourceIdentifier": "[email protected]",
"published": "2026-04-10T16:16:31.070",
"lastModified": "2026-10-26T22:10:00.163",
"vulnStatus": "Analyzed",
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"value": "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.\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."
},
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"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 inyección de registros a través de secuencias CRLF debido a cambios de nombre no documentados de atributos de configuración 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 provocó que el escape de nueva línea dejara de funcionar para los usuarios de tramas TCP (RFC 6587), exponiéndolos a la inyección de CRLF en la salida de registros.\n * El atributo useTlsMessageFormat fue renombrado silenciosamente, lo que provocó que los usuarios de tramas TLS (RFC 5425) fueran degradados silenciosamente a TCP sin tramas (RFC 6587), sin escape de nueva línea.\n\nLos usuarios del SyslogAppender no se ven afectados, ya que sus atributos de configuración no fueron modificados.\n\nSe aconseja a los usuarios actualizar a Apache Log4j Core 2.25.4, que corrige este problema."
}
],
"affected": [
{
"source": "[email protected]",
"affectedData": [
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"vendor": "Apache Software Foundation",
"product": "Apache Log4j Core",
"defaultStatus": "unaffected",
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"exploitMaturity": "NOT_DEFINED",
"confidentialityRequirement": "NOT_DEFINED",
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"modifiedAttackVector": "NOT_DEFINED",
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"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",
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"type": "Primary",
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"id": "CVE-2026-34478",
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"version": "2.0.3"
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"weaknesses": [
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"source": "[email protected]",
"type": "Secondary",
"description": [
{
"lang": "en",
"value": "CWE-117"
},
{
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"value": "CWE-684"
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"url": "https://github.com/apache/logging-log4j2/pull/4074",
"source": "[email protected]",
"tags": [
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