Apache log4net: NUL character truncates EventLogAppender records

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-105239
StatePUBLISHED
Assignerapache
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-06 20:17:15 UTC
Updated2026-10-06 20:17:15 UTC
DescriptionImproper 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.

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-158 | CWE-158 CWE-158 Improper Neutralization of Null Byte or NUL Character

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 1.2.9 3.5.0 semver Not specified
CNA Apache Software Foundation Apache Log4net affected 02e1e115435888485f2e28b414d267e39e799e07 dc5855a0720c91590fd7a81d729ea01fdd69e000 git Not specified

References

ReferenceSourceLinkTags
lists.apache.org/thread.html/9fx1qo5hc0tg8ym0t6p9gt1zpb2qlxpq [email protected] lists.apache.org
github.com/apache/logging-log4net/pull/315 [email protected] github.com
github.com/apache/logging-log4net/commit/dc5855a0720c91590fd7a81d729ea01... [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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