CVE-2026-105244

MEDIUM 5.3

Apache log4net: RemoteSyslogAppender silently deletes non-ASCII content

CVSS Score

5.3

EPSS Score

0.0%

EPSS Percentile

0th

Improper Encoding or Escaping of Output vulnerability in the RemoteSyslogAppender of Apache log4net. Every character outside visible ASCII and space was removed from the record instead of being escaped, so non-ASCII text and control characters such as tabs disappeared without notice. A party whose data reaches a log message could make a distinct value look identical in the record, for example a user name holding a zero-width space logged as admin. Only applications that use RemoteSyslogAppender are affected. This issue affects Apache log4net: from 1.2.12 before 3.5.0. Users are recommended to upgrade to version 3.5.0, which fixes the issue.

CWE	CWE-116
Vendor	apache software foundation
Product	apache log4net
Published	Oct 6, 2026

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CVSS v3 Breakdown

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

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

Low

Availability

None

Affected Versions

Apache Software Foundation / Apache log4net

1.2.12 < 3.5.0

Apache Software Foundation / Apache log4net

56a2e146e21ff4737e1ff3ec308810e667873947 < 77717061b20d4346b6c0ce6b54643d85fb348bc7

References

NVD ↗ CVE.org ↗ EPSS Data ↗

github.com: https://github.com/apache/logging-log4net/pull/315 github.com: https://github.com/apache/logging-log4net/commit/77717061b20d4346b6c0ce6b54643d85fb348bc7 lists.apache.org: https://lists.apache.org/thread.html/q7649hhdodthoqw8jsjgtnb4m8qfy6d6

Credits

The Apache Software Foundation Claude Security Jan Friedrich