{"id":"CVE-2026-105243","title":"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…","summary":"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…","severity":"medium","cvss":5.3,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N","cwe":["CWE-778"],"vendor":"Apache Software Foundation","product":"log4net","affected":["log4net >= 1.2.9 < 3.5.0","log4net >= 02e1e115435888485f2e28b414d267e39e799e07 < 28fbfb25678c48a8cc5bc9b94ead0dddfc39ffed"],"published":"2026-10-06","updated":"2026-10-06","sourceUpdated":"2026-10-06T20:17:16.167","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-105243","references":[{"url":"https://github.com/apache/logging-log4net/commit/28fbfb25678c48a8cc5bc9b94ead0dddfc39ffed","label":"security@apache.org"},{"url":"https://github.com/apache/logging-log4net/pull/315","label":"security@apache.org"},{"url":"https://lists.apache.org/thread.html/jr6fj5skv1vnjbc9jmt8bp151p8ow1rp","label":"security@apache.org"}],"tags":["nvd","cve.org"],"ingestedAt":"2026-10-06T20:16:42.475Z","slug":"CVE-2026-105243","body":"## Overview\n\nInsufficient 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.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":29,"depthScoreParts":{"impact":29.2,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}