CVE-2026-105240
mediumImproper Neutralization of Null Byte or NUL Character vulnerability in the OutputDebugStringAppender of Apache log4net.
Vendor / product: Apache — log4net
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.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N Affected products
Weakness classification (CWE)
Source: NVD / CISA. “NVD-CWE-Other” and “NVD-CWE-noinfo” mean NVD could not assign a specific weakness.
Mitigation & advisories
References
- https://github.com/apache/logging-log4net/commit/6046fe9d7f353b49fe995361c071ec2eea8f7ef6 security@apache.org
- https://github.com/apache/logging-log4net/pull/315 security@apache.org
- https://lists.apache.org/thread.html/gyw2d4ppy82t1vlpdknkfd1nmzp21z17 security@apache.org
- http://www.openwall.com/lists/oss-security/2026/10/07/18 af854a3a-2127-422b-91ae-364da2661108