{"id":"CVE-2026-105243","summary":"Apache log4net: Oversize EventLogAppender record silently discarded","details":"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.","modified":"2026-10-08T02:51:15.440167364Z","published":"2026-10-06T19:51:25.116Z","database_specific":{"cwe_ids":["CWE-778"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/105xxx/CVE-2026-105243.json","cna_assigner":"apache"},"references":[{"type":"WEB","url":"http://www.openwall.com/lists/oss-security/2026/10/07/17"},{"type":"WEB","url":"https://nuget.org/packages"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/105xxx/CVE-2026-105243.json"},{"type":"ADVISORY","url":"https://lists.apache.org/thread.html/jr6fj5skv1vnjbc9jmt8bp151p8ow1rp"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-105243"},{"type":"FIX","url":"https://github.com/apache/logging-log4net/commit/28fbfb25678c48a8cc5bc9b94ead0dddfc39ffed"},{"type":"FIX","url":"https://github.com/apache/logging-log4net/pull/315"},{"type":"PACKAGE","url":"https://gitbox.apache.org/repos/asf/logging-log4net.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://gitbox.apache.org/repos/asf/logging-log4net.git","events":[{"introduced":"02e1e115435888485f2e28b414d267e39e799e07"},{"fixed":"28fbfb25678c48a8cc5bc9b94ead0dddfc39ffed"}]},{"type":"GIT","repo":"https://github.com/apache/logging-log4net","events":[{"introduced":"18a96716af733f7c6e4956526acdcc117a1bd461"},{"fixed":"f7794ae187ab2e228e1754cb478568dd305d1b32"},{"fixed":"28fbfb25678c48a8cc5bc9b94ead0dddfc39ffed"}],"database_specific":{"extracted_events":[{"introduced":"1.2.9"},{"fixed":"3.5.0"}],"source":["DESCRIPTION","REFERENCES"]}}],"versions":["rc/3.4.1-preview.1","rel/3.4.0","rc/3.4.0-rc1","rc/3.4.0-preview.1","rel/3.3.2","rc/3.3.2-rc1","rel/3.3.1","rc/3.3.1-rc1","rel/3.3.0","rc/3.3.0-rc1","rc/3.2.0-rc1","rc/temp","rel/3.2.0","rc/3.2.0-preview.1","rel/3.1.0","rc/3.1.0-rc1","rel/3.0.4","rc/3.0.4-rc1","rc/3.0.4-preview.1","rel/3.0.3","rc/3.0.3-rc1","rc/3.0.3-preview.1","rel/3.0.2","rc/3.0.2-rc1","rel/3.0.1","rc/3.0.1-rc1","rc/3.0.1-preview.2","rc/3.0.1-preview.1","rel/2.x","rel/2.0.17","rel/2.0.16","rel/2.0.15","rel/2.0.14","rel/2.0.13","rel/2.0.12","rel/2.0.11","rel/2.0.10"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-105243.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N"}]}