{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-105243","assignerOrgId":"f0158376-9dc2-43b6-827c-5f631a4d8d09","state":"PUBLISHED","assignerShortName":"apache","dateReserved":"2026-10-04T16:21:38.272Z","datePublished":"2026-10-06T19:51:25.116Z","dateUpdated":"2026-10-07T14:49:41.976Z"},"containers":{"cna":{"providerMetadata":{"orgId":"f0158376-9dc2-43b6-827c-5f631a4d8d09","shortName":"apache","dateUpdated":"2026-10-06T19:51:25.116Z"},"title":"Apache log4net: Oversize EventLogAppender record silently discarded","problemTypes":[{"descriptions":[{"description":"CWE-778 Insufficient Logging","lang":"en","cweId":"CWE-778","type":"CWE"}]}],"source":{"discovery":"INTERNAL"},"affected":[{"vendor":"Apache Software Foundation","product":"Apache log4net","packageURL":"pkg:nuget/log4net","versions":[{"status":"affected","version":"1.2.9","lessThan":"3.5.0","versionType":"semver"}],"defaultStatus":"unaffected","collectionURL":"https://nuget.org/packages","packageName":"log4net"},{"vendor":"Apache Software Foundation","product":"Apache log4net","packageURL":"pkg:nuget/log4net","repo":"https://gitbox.apache.org/repos/asf/logging-log4net.git","versions":[{"status":"affected","version":"02e1e115435888485f2e28b414d267e39e799e07","lessThan":"28fbfb25678c48a8cc5bc9b94ead0dddfc39ffed","versionType":"git"}],"defaultStatus":"unaffected","collectionURL":"https://nuget.org/packages","packageName":"log4net"}],"descriptions":[{"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. 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.","lang":"en","supportingMedia":[{"type":"text/html","base64":false,"value":"Insufficient Logging vulnerability in the EventLogAppender of Apache log4net.<br><br>Long 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.<br><br>This issue affects Apache log4net: from 1.2.9 before 3.5.0.<br><br>Users are recommended to upgrade to version 3.5.0, which fixes the issue."}]}],"references":[{"url":"https://github.com/apache/logging-log4net/pull/315","tags":["patch"]},{"url":"https://github.com/apache/logging-log4net/commit/28fbfb25678c48a8cc5bc9b94ead0dddfc39ffed","tags":["patch"]},{"url":"https://lists.apache.org/thread.html/jr6fj5skv1vnjbc9jmt8bp151p8ow1rp","tags":["vendor-advisory"]}],"metrics":[{"other":{"type":"Textual description of severity","content":{"text":"moderate"}},"scenarios":[{"lang":"en","value":"GENERAL"}]},{"scenarios":[{"lang":"en","value":"GENERAL"}],"format":"CVSS","cvssV3_1":{"version":"3.1","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"NONE","integrityImpact":"LOW","availabilityImpact":"NONE","baseSeverity":"MEDIUM","baseScore":5.3,"vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N"}}],"credits":[{"lang":"en","value":"The Apache Software Foundation","type":"finder"},{"lang":"en","value":"Claude Security","type":"tool"},{"lang":"en","value":"Jan Friedrich","type":"remediation developer"}],"x_generator":{"engine":"Vulnogram 1.0.3"}},"adp":[{"title":"CVE Program Container","references":[{"url":"http://www.openwall.com/lists/oss-security/2026/10/07/17"}],"providerMetadata":{"orgId":"af854a3a-2127-422b-91ae-364da2661108","shortName":"CVE","dateUpdated":"2026-10-07T06:11:59.799Z"}},{"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-10-07T14:49:30.641089Z","id":"CVE-2026-105243","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"title":"CISA ADP Vulnrichment","providerMetadata":{"orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","shortName":"CISA-ADP","dateUpdated":"2026-10-07T14:49:41.976Z"}}]}}