Improper Neutralization of Null Byte or NUL Character vulnerability in the OutputDebugStringAppender of Apache log4net. A NUL character in logged content ended the debug output record at that point, so everything the layout rendered after it, including exception text and trailing fields, was silently lost. A party whose data reaches a log message could hide the rest of that record. Only applications on Windows that use OutputDebugStringAppender 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.
Fix
Patch, vendor advisory and mitigation references on NVD 3
- https://github.com/apache/logging-log4net/commit/6046fe9d7f353b49fe995361c071ec2eea8f7ef6 Patch
- https://github.com/apache/logging-log4net/pull/315 Patch
- https://lists.apache.org/thread.html/gyw2d4ppy82t1vlpdknkfd1nmzp21z17 Mailing List, Vendor Advisory
Every line above is quoted from NVD, CISA, Microsoft, the vendor's own advisory or DISA; nothing is generated.
Change history 1
- First seenCVSS 5.3 · apacheNVD modified 2026-10-09 15:41
Affected (CPE criteria) 1
cpe:2.3:a:apache:log4net:*:*:*:*:*:*:*:*
References 4
- https://github.com/apache/logging-log4net/commit/6046fe9d7f353b49fe995361c071ec2eea8f7ef6 Patch
- https://github.com/apache/logging-log4net/pull/315 Patch
- https://lists.apache.org/thread.html/gyw2d4ppy82t1vlpdknkfd1nmzp21z17 Mailing List, Vendor Advisory
- http://www.openwall.com/lists/oss-security/2026/10/07/18 Mailing List, Third Party Advisory