Description
Improper 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.
Published: 2026-10-06
Score: 5.3 Medium
EPSS: < 1% Very Low
KEV: No
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Remediation

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History

Wed, 07 Oct 2026 07:30:00 +0000

Type Values Removed Values Added
References

Wed, 07 Oct 2026 00:00:00 +0000

Type Values Removed Values Added
First Time appeared Apache
Apache log4net
Vendors & Products Apache
Apache log4net

Tue, 06 Oct 2026 20:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

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


Tue, 06 Oct 2026 20:00:00 +0000

Type Values Removed Values Added
Description Improper 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.
Title Apache log4net: NUL character truncates EventLogAppender records
Weaknesses CWE-158
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'}


cve-icon MITRE

Status: PUBLISHED

Assigner: apache

Published:

Updated: 2026-10-07T06:11:55.256Z

Reserved: 2026-10-04T16:19:29.460Z

Link: CVE-2026-105239

cve-icon Vulnrichment

Updated: 2026-10-07T06:11:55.256Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-10-06T20:17:15.630

Modified: 2026-10-07T13:35:14.410

Link: CVE-2026-105239

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-10-07T00:45:09Z

Weaknesses
  • CWE-158

    Improper Neutralization of Null Byte or NUL Character