Vulnerability in Apache Software Foundation Apache log4net

[ Description ]Official description

Insufficient Logging vulnerability in the EventLogAppender of Apache log4net. 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. This issue affects Apache log4net: from 1.2.9 before 3.5.0. Users are recommended to upgrade to version 3.5.0, which fixes the issue.

[ Fixes ]Fixes and patches

• Patch on github.comVendor patch or bulletin · NVD · Reference tagged 'Patch' by NVD
• Patch on github.comVendor patch or bulletin · NVD · Reference tagged 'Patch' by NVD

[ Advisories ]Government CERT advisories

• BSI CERT-Bund6 Oct 2026WID-SEC-2026-3772

  Apache log4net: Multiple vulnerabilities allow file manipulation Translated from German

  CVE-2026-105240CVE-2026-105239CVE-2026-105243+3 more CVEs

[ References ]References

• github.com/apache/logging-log4net/commit/28fbfb25678c48a8cc5bc9b94ead0dddfc39ffedPatch
• github.com/apache/logging-log4net/pull/315Patch
• lists.apache.org/thread.html/jr6fj5skv1vnjbc9jmt8bp151p8ow1rpMailing ListVendor Advisory
• www.openwall.com/lists/oss-security/2026/10/07/17Mailing ListThird Party Advisory