FKIE_CVE-2026-34480

Vulnerability from fkie_nvd - Published: 2026-04-10 16:16 - Updated: 2026-04-24 18:21
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 XmlLayout https://logging.apache.org/log4j/2.x/manual/layouts.html#XmlLayout , in versions up to and including 2.25.3, fails to sanitize characters forbidden by the XML 1.0 specification https://www.w3.org/TR/xml/#charsets producing invalid XML output whenever a log message or MDC value contains such characters. The impact depends on the StAX implementation in use: * JRE built-in StAX: Forbidden characters are silently written to the output, producing malformed XML. Conforming parsers must reject such documents with a fatal error, which may cause downstream log-processing systems to drop the affected records. * Alternative StAX implementations (e.g., Woodstox https://github.com/FasterXML/woodstox , a transitive dependency of the Jackson XML Dataformat module): An exception is thrown during the logging call, and the log event is never delivered to its intended appender, only to Log4j's internal status logger. Users are advised to upgrade to Apache Log4j Core 2.25.4, which corrects this issue by sanitizing forbidden characters before XML output.
References
security@apache.orghttps://github.com/apache/logging-log4j2/pull/4077Issue Tracking, Patch
security@apache.orghttps://lists.apache.org/thread/5x0hcnng0chhghp6jgjdp3qmbbhfjzhbMailing List, Vendor Advisory
security@apache.orghttps://logging.apache.org/cyclonedx/vdr.xmlProduct
security@apache.orghttps://logging.apache.org/log4j/2.x/manual/layouts.html#XmlLayoutTechnical Description
security@apache.orghttps://logging.apache.org/security.html#CVE-2026-34480Vendor Advisory
af854a3a-2127-422b-91ae-364da2661108http://www.openwall.com/lists/oss-security/2026/04/10/9Mailing 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
apache log4j 3.0.0
apache log4j 3.0.0
apache log4j 3.0.0
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      "value": "Apache Log4j Core\u0027s  XmlLayout https://logging.apache.org/log4j/2.x/manual/layouts.html#XmlLayout , in versions up to and including 2.25.3, fails to sanitize characters forbidden by the  XML 1.0 specification https://www.w3.org/TR/xml/#charsets  producing invalid XML output whenever a log message or MDC value contains such characters.\n\nThe impact depends on the StAX implementation in use:\n\n  *  JRE built-in StAX: Forbidden characters are silently written to the output, producing malformed XML. Conforming parsers must reject such documents with a fatal error, which may cause downstream log-processing systems to drop the affected records.\n  *  Alternative StAX implementations (e.g.,  Woodstox https://github.com/FasterXML/woodstox , a transitive dependency of the Jackson XML Dataformat module): An exception is thrown during the logging call, and the log event is never delivered to its intended appender, only to Log4j\u0027s internal status logger.\n\n\nUsers are advised to upgrade to Apache Log4j Core 2.25.4, which corrects this issue by sanitizing forbidden characters before XML output."
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  "lastModified": "2026-04-24T18:21:54.990",
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Detection rules are retrieved from Rulezet.