Improper Handling of Unicode Encoding 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.
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Test your applications- Snyk IDSNYK-DEBIAN13-LOG4NET-20562051
- published7 Oct 2026
- disclosed6 Oct 2026
Introduced: 6 Oct 2026
NewCVE-2026-105241 (opens in a new tab)How to fix?
There is no fixed version for Debian:13 log4net.
NVD Description
Note: Versions mentioned in the description apply only to the upstream log4net package and not the log4net package as distributed by Debian.
See How to fix? for Debian:13 relevant fixed versions and status.
Improper Handling of Unicode Encoding vulnerability in the SmtpPickupDirAppender of Apache log4net.
Content that the mail file writer cannot encode, such as an unpaired UTF-16 surrogate, made the write throw. Every buffered event in the batch was discarded, not only the one carrying the content, and a truncated mail could be left in the pickup directory. A party whose data reaches a log message could suppress the records of other events. Only applications that use SmtpPickupDirAppender 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://security-tracker.debian.org/tracker/CVE-2026-105241
- https://github.com/apache/logging-log4net/commit/4d2e10f0908199604b4326f9df6d0b43b871e333
- https://github.com/apache/logging-log4net/pull/315
- https://lists.apache.org/thread.html/hg8dgh3oy8bp3dhb8nsygk9kw2o401ws
- http://www.openwall.com/lists/oss-security/2026/10/07/15