CVE-2026-105239

Apache log4net: NUL character truncates EventLogAppender records

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

Remediation

No solution or workaround provided in the CVE record

Tracking

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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 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'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
apache
Published
Updated
Oct 7, 2026, 6:11 AM
Reserved
Oct 4, 2026, 4:19 PM
Status
Analyzed
Published
Oct 6, 2026, 8:17 PM
Modified
Oct 9, 2026, 3:44 PM