CVE-2026-105240

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

5.3CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

EPSS

0.8% chance of exploitation in the next 30 days; higher than 56% of CVEs (scores of 2026-10-25)

CWE

CWE-158

Published

2026-10-06

Modified

2026-10-09

Record from

the NVD, synced 2026-10-19

Affected

• apache:log4net

References

• https://github.com/apache/logging-log4net/commit/6046fe9d7f353b49fe995361c071ec2eea8f7ef6
• https://github.com/apache/logging-log4net/pull/315
• https://lists.apache.org/thread.html/gyw2d4ppy82t1vlpdknkfd1nmzp21z17
• http://www.openwall.com/lists/oss-security/2026/10/07/18

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