Improper Handling of Exceptional Conditions vulnerability in the aspnet-request pattern converter of Apache log4net. Reading request parameters triggers ASP.NET request validation, so a request carrying content such as markup made the layout throw and the appender discarded the whole event. A sender could suppress the log record of their own request. Only applications on ASP.NET for .NET Framework whose layout uses %aspnet-request are affected. This issue affects Apache log4net: from 1.2.11 before 3.5.0. Users are recommended to upgrade to version 3.5.0, which fixes the issue.
Fix
Patch, vendor advisory and mitigation references on NVD 3
- https://github.com/apache/logging-log4net/commit/145203420c579a703008b4b723b6a080757f4964 Patch
- https://github.com/apache/logging-log4net/pull/316 Patch
- https://lists.apache.org/thread.html/zg6dbqm4ztm7j3c21nfsqj0yxm5yrpdx Mailing List, Vendor Advisory
Every line above is quoted from NVD, CISA, Microsoft, the vendor's own advisory or DISA; nothing is generated.
Change history 1
- First seenCVSS 5.3 · apacheNVD modified 2026-10-09 15:28
Affected (CPE criteria) 1
cpe:2.3:a:apache:log4net:*:*:*:*:*:*:*:*
References 4
- https://github.com/apache/logging-log4net/commit/145203420c579a703008b4b723b6a080757f4964 Patch
- https://github.com/apache/logging-log4net/pull/316 Patch
- https://lists.apache.org/thread.html/zg6dbqm4ztm7j3c21nfsqj0yxm5yrpdx Mailing List, Vendor Advisory
- http://www.openwall.com/lists/oss-security/2026/10/07/16 Mailing List, Third Party Advisory