{"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","product":"log4net","affected":["log4net >= 1.2.9, < 3.5.0"],"patched":["log4net 3.5.0"],"published":"2026-10-06","updated":"2026-10-09","sourceUpdated":"2026-10-09T15:26:03.430","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"},{"url":"http://www.openwall.com/lists/oss-security/2026/10/07/17","label":"af854a3a-2127-422b-91ae-364da2661108"}],"tags":["nvd","cve.org"],"epss":0.00807,"epssPercentile":0.56638,"ssvc":{"exploitation":"none","automatable":"yes","technicalImpact":"partial","timestamp":"2026-10-07T14:49:30.641089Z"},"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## Affected\n\n- `log4net >= 1.2.9, < 3.5.0`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `log4net 3.5.0`","depth":"sunlit","depthScore":29,"depthScoreParts":{"impact":29.2,"likelihood":0.2,"exploitation":0,"ransomware":0},"changes":[]}