{"id":"CVE-2026-105243","state":"PUBLISHED","title":"Apache log4net: Oversize EventLogAppender record silently discarded","description":"Insufficient Logging vulnerability in the EventLogAppender of Apache log4net.\n\nLong messages were truncated to a fixed size that exceeds what the Windows Event Log accepts once the log and source names are counted, and the event log then stored nothing and reported nothing. A party whose data reaches a log message could suppress the whole record by making it long enough. Only applications on Windows that use EventLogAppender are affected.\n\nThis issue affects Apache log4net: from 1.2.9 before 3.5.0.\n\nUsers are recommended to upgrade to version 3.5.0, which fixes the issue.","publishedAt":"2026-10-06T19:51:25.116Z","updatedAt":"2026-10-07T14:49:41.976Z","severity":{"score":5.3,"label":"Medium","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N","source":"apache"},"assigner":"apache","products":["Apache Software Foundation Apache log4net"],"affected":[{"vendor":"Apache Software Foundation","product":"Apache log4net","packageName":"log4net","packageURL":"pkg:nuget/log4net","defaultStatus":"unaffected","versions":[{"version":"1.2.9","status":"affected","lessThan":"3.5.0","versionType":"semver"}],"collectionURL":"https://nuget.org/packages"},{"vendor":"Apache Software Foundation","product":"Apache log4net","packageName":"log4net","packageURL":"pkg:nuget/log4net","defaultStatus":"unaffected","versions":[{"version":"02e1e115435888485f2e28b414d267e39e799e07","status":"affected","lessThan":"28fbfb25678c48a8cc5bc9b94ead0dddfc39ffed","versionType":"git"}],"repo":"https://gitbox.apache.org/repos/asf/logging-log4net.git","collectionURL":"https://nuget.org/packages"}],"references":["https://github.com/apache/logging-log4net/pull/315","https://github.com/apache/logging-log4net/commit/28fbfb25678c48a8cc5bc9b94ead0dddfc39ffed","https://lists.apache.org/thread.html/jr6fj5skv1vnjbc9jmt8bp151p8ow1rp","http://www.openwall.com/lists/oss-security/2026/10/07/17"],"weaknesses":["CWE-778"],"ingestedAt":"2026-10-29T20:10:23.711Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/105xxx/CVE-2026-105243.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-105243","state":"PUBLISHED","datePublished":"2026-10-06T19:51:25.116Z","dateUpdated":"2026-10-07T14:49:41.976Z","assignerShortName":"apache","assignerOrgId":"f0158376-9dc2-43b6-827c-5f631a4d8d09","dateReserved":"2026-10-04T16:21:38.272Z"},"containers":{"cna":{"title":"Apache log4net: Oversize EventLogAppender record silently discarded","descriptions":[{"lang":"en","value":"Insufficient Logging vulnerability in the EventLogAppender of Apache log4net.\n\nLong messages were truncated to a fixed size that exceeds what the Windows Event Log accepts once the log and source names are counted, and the event log then stored nothing and reported nothing. 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