Improper Neutralization of Null Byte or NUL Character Affecting log4net package, versions *
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
Do your applications use this vulnerable package?
In a few clicks we can analyze your entire application and see what components are vulnerable in your application, and suggest you quick fixes.
Test your applications- Snyk IDSNYK-ECHOLATEST-LOG4NET-20557218
- published7 Oct 2026
- disclosed6 Oct 2026
Introduced: 6 Oct 2026
NewCVE-2026-105240 (opens in a new tab)How to fix?
There is no fixed version for Echo:latest log4net.
NVD Description
Note: Versions mentioned in the description apply only to the upstream log4net package and not the log4net package as distributed by Echo.
See How to fix? for Echo:latest relevant fixed versions and status.
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.
References
- https://advisory.echohq.com/cve/CVE-2026-105240
- 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