Apache log4net: RemoteSyslogAppender silently deletes non-ASCII content

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-105244
StatePUBLISHED
Assignerapache
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-06 20:17:16 UTC
Updated2026-10-06 20:17:16 UTC
DescriptionImproper 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.

Risk And Classification

Primary CVSS: v3.1 5.3 MEDIUM from [email protected]

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

Problem Types: CWE-116 | CWE-116 CWE-116 Improper Encoding or Escaping of Output

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary5.3MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
3.1CNACVSS5.3MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
None

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Apache Software Foundation Apache Log4net affected 1.2.12 3.5.0 semver Not specified
CNA Apache Software Foundation Apache Log4net affected 56a2e146e21ff4737e1ff3ec308810e667873947 77717061b20d4346b6c0ce6b54643d85fb348bc7 git Not specified

References

ReferenceSourceLinkTags
lists.apache.org/thread.html/q7649hhdodthoqw8jsjgtnb4m8qfy6d6 [email protected] lists.apache.org
github.com/apache/logging-log4net/commit/77717061b20d4346b6c0ce6b54643d8... [email protected] github.com
github.com/apache/logging-log4net/pull/315 [email protected] github.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: The Apache Software Foundation (en)

CNA: Claude Security (en)

CNA: Jan Friedrich (en)

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