CVE-2026-105244

Apache log4net: RemoteSyslogAppender silently deletes non-ASCII content

Published Oct 6, 2026 CVSS 3.1 · 5.3 Medium EPSS < 1% KEV · Not listed
Description
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

Sign in to view the affected projects.

Advisories

No advisories available
History
Type Values Removed Values Added
CPEs cpe:2.3:a:apache:log4net:*:*:*:*:*:*:*:*
Type Values Removed Values Added
First Time appeared Apache
Apache log4net
Vendors & Products Apache
Apache log4net
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
Description 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.
Title Apache log4net: RemoteSyslogAppender silently deletes non-ASCII content
Weaknesses CWE-116
References
Metrics cvssV3_1

{'score': 5.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
apache
Published
Updated
Oct 7, 2026, 2:50 PM
Reserved
Oct 4, 2026, 4:22 PM
Status
Analyzed
Published
Oct 6, 2026, 8:17 PM
Modified
Oct 9, 2026, 3:18 PM