Insufficient Logging vulnerability in the EventLogAppender of Apache log4net. Long messages were truncated to a fixed size that exceeds what the Windows Event Log accepts once the log and source names are counted, and the event log then stored nothing and reported nothing. A party whose data reaches a log message could suppress the whole record by making it long enough. 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.
History

Fri, 09 Oct 2026 15:45:00 +0000

Type Values Removed Values Added
CPEs cpe:2.3:a:apache:log4net:*:*:*:*:*:*:*:*

Thu, 08 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'}


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

Type Values Removed Values Added
References

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

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First Time appeared Apache
Apache log4net
Vendors & Products Apache
Apache log4net

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

Type Values Removed Values Added
Description Insufficient Logging vulnerability in the EventLogAppender of Apache log4net. Long messages were truncated to a fixed size that exceeds what the Windows Event Log accepts once the log and source names are counted, and the event log then stored nothing and reported nothing. A party whose data reaches a log message could suppress the whole record by making it long enough. 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: Oversize EventLogAppender record silently discarded
Weaknesses CWE-778
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: 2026-10-06T19:51:25.116Z

Updated: 2026-10-07T14:49:41.976Z

Reserved: 2026-10-04T16:21:38.272Z

Link: CVE-2026-105243

cve-icon Vulnrichment

Updated: 2026-10-07T06:11:59.799Z

cve-icon NVD

Status : Analyzed

Published: 2026-10-06T20:17:16.167

Modified: 2026-10-09T15:26:03.430

Link: CVE-2026-105243

cve-icon Redhat

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