{"id":"CVE-2026-105243","revision":"7c4da6b59c16497bb6dca659503ab220","records":[{"revision":"7c4da6b59c16497bb6dca659503ab220","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-105243","aliases":[],"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.","state":0,"publishedAt":"2026-10-06T19:51:25.116+00:00","modifiedAt":"2026-10-07T14:49:41.976+00:00","affected":[{"ecosystem":"NuGet","name":"log4net","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"vendor\": \"Apache Software Foundation\",\n                    \"product\": \"Apache log4net\",\n                    \"packageURL\": \"pkg:nuget/log4net\",\n                    \"versions\": [\n                        {\n                            \"status\": \"affected\",\n                            \"version\": \"1.2.9\",\n                            \"lessThan\": \"3.5.0\",\n                            \"versionType\": \"semver\"\n                        }\n                    ],\n                    \"defaultStatus\": \"unaffected\",\n                    \"collectionURL\": \"https://nuget.org/packages\",\n                    \"packageName\": \"log4net\"\n                }"},{"ecosystem":"NuGet","name":"log4net","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"vendor\": \"Apache Software Foundation\",\n                    \"product\": \"Apache log4net\",\n                    \"packageURL\": \"pkg:nuget/log4net\",\n                    \"repo\": \"https://gitbox.apache.org/repos/asf/logging-log4net.git\",\n                    \"versions\": [\n                        {\n                            \"status\": \"affected\",\n                            \"version\": \"02e1e115435888485f2e28b414d267e39e799e07\",\n                            \"lessThan\": \"28fbfb25678c48a8cc5bc9b94ead0dddfc39ffed\",\n                            \"versionType\": \"git\"\n                        }\n                    ],\n                    \"defaultStatus\": \"unaffected\",\n                    \"collectionURL\": \"https://nuget.org/packages\",\n                    \"packageName\": \"log4net\"\n                }"}],"metrics":[{"system":"CVSS 3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N","score":5.3,"severity":"MEDIUM"}],"references":["https://github.com/apache/logging-log4net/pull/315","https://github.com/apache/logging-log4net/commit/28fbfb25678c48a8cc5bc9b94ead0dddfc39ffed","https://lists.apache.org/thread.html/jr6fj5skv1vnjbc9jmt8bp151p8ow1rp"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-105243","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-105243","identifiers":["CVE-2026-105243"]},"retained":false,"historicalAffected":[]}],"coverage":[]}