{"id":"EUVD-2026-21488","revision":"0762e8deb97a4d72849dd1c6f92bb2cc","records":[{"revision":"0762e8deb97a4d72849dd1c6f92bb2cc","observedAt":"2026-10-28T05:00:35.764+00:00","statement":{"source":"euvd","id":"EUVD-2026-21488","aliases":["CVE-2026-40021","GHSA-4f7c-pmjv-c25w"],"title":"Apache Log4net's  XmlLayout https://logging.apache.org/log4net/manual/configuration/layouts.html#layout-list  and  XmlLayoutSchemaLog4J https://logging.apache.org/log4net/manual/configuration/layouts.html#layout-list , in versions before 3.…","description":"Apache Log4net's  XmlLayout https://logging.apache.org/log4net/manual/configuration/layouts.html#layout-list  and  XmlLayoutSchemaLog4J https://logging.apache.org/log4net/manual/configuration/layouts.html#layout-list , in versions before 3.3.0, fail to sanitize characters forbidden by the  XML 1.0 specification https://www.w3.org/TR/xml/#charsets  in MDC property keys and values, as well as the identity field that may carry attacker-influenced data. This causes an exception during serialization and the silent loss of the affected log event.\n\nAn attacker who can influence any of these fields can exploit this to suppress individual log records, impairing audit trails and detection of malicious activity.\n\nUsers are advised to upgrade to Apache Log4net 3.3.0, which fixes this issue.","state":0,"publishedAt":null,"modifiedAt":null,"affected":[],"metrics":[{"system":"EUVD CVSS 4.0","vector":"CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N","score":6.3,"severity":null}],"references":["https://github.com/apache/logging-log4net/pull/280","https://logging.apache.org/security.html#CVE-2026-40021","https://logging.apache.org/cyclonedx/vdr.xml","https://logging.apache.org/log4net/manual/configuration/layouts.html","https://lists.apache.org/thread/q8otftjswhk69n3kxslqg7cobr0x4st7"],"sourceUrl":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-21488","license":"ENISA EUVD · source terms and attribution apply","enrichment":{"sourceStatus":null,"weaknesses":[],"productCriteria":[],"sourceDates":{"datePublished":"Apr 10, 2026, 3:44:17 PM","dateUpdated":"Apr 10, 2026, 5:35:01 PM"},"relatedAdvisories":[{"id":"WID-SEC-W-2026-1054","title":"Apache log4net: Schwachstelle ermöglicht Manipulation von Dateien","vulnerabilityIds":["CVE-2026-40021"]}],"note":"EUVD source date text has no stated timezone and is retained without inventing a UTC instant. Related bulletin membership is not an alias, common cause or applicability claim. A missing vector with a zero score is treated as unrated. Complete vendor/product and underlying source evidence remains in the original JSON."},"key":"euvd:EUVD-2026-21488","identifiers":["EUVD-2026-21488","CVE-2026-40021","GHSA-4f7c-pmjv-c25w"]},"retained":false,"historicalAffected":[]}],"coverage":[]}