CVE-2026-105239

Name	CVE-2026-105239
Description	Improper Neutralization of Null Byte or NUL Character vulnerability in the EventLogAppender of Apache log4net. A NUL character in logged content ended the Windows Event Log record at that point, so everything the layout rendered after it, including exception text and trailing fields, was silently not stored. A party whose data reaches a log message could hide the rest of that record. 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.
Source	CVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
log4net (PTS)	trixie	1.2.10+dfsg-9	vulnerable
	forky, sid	1.2.10+dfsg-10	vulnerable

The information below is based on the following data on fixed versions.

Package	Type	Release	Fixed Version	Urgency	Origin	Debian Bugs
log4net	source	(unstable)	(unfixed)

Notes

https://github.com/apache/logging-log4net/pull/315
Fixed by: https://github.com/apache/logging-log4net/commit/dc5855a0720c91590fd7a81d729ea01fdd69e000 (rc/3.5.0-rc1)
https://lists.apache.org/thread/9fx1qo5hc0tg8ym0t6p9gt1zpb2qlxpq