Improper Handling of Exceptional Conditions vulnerability in the aspnet-request pattern converter of Apache log4net. (CVE-2026-105242)
Description
An improper handling of exceptional conditions vulnerability exists in the aspnet-request pattern converter of Apache log4net. When reading request parameters, ASP.NET request validation can cause the layout to throw an exception if the request contains markup content, resulting in the appender discarding the entire log event. This allows a sender to suppress logging of their own request. The issue affects applications running on ASP.NET for .NET Framework that use the %aspnet-request layout pattern. The vulnerability is fixed in log4net version 3.5.0.
CVSS v3.1
Score 5.3medium
Affected software
pkg:deb/ubuntu/log4net?arch=source&distro=xenialpkg:deb/ubuntu/log4net?arch=source&distro=bionicpkg:deb/ubuntu/log4net?arch=source&distro=focalpkg:deb/ubuntu/log4net?arch=source&distro=jammypkg:deb/ubuntu/log4net?arch=source&distro=noblepkg:deb/ubuntu/log4net?arch=source&distro=stonkingpkg:deb/ubuntu/log4net?arch=source&distro=resoluteRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-105242 describes a vulnerability in Apache log4net's aspnet-request pattern converter where improper handling of exceptional conditions causes the logging layout to throw an exception when processing request parameters containing markup. This leads to the appender discarding the entire log event, allowing an attacker to suppress log records of their own requests. The vulnerability affects log4net versions from 1.2.11 up to but not including 3.5.0, specifically in ASP.NET applications using the %aspnet-request layout. The issue is resolved by upgrading to version 3.5.0.
Potential Impact
The vulnerability allows an attacker to suppress logging of their own requests by triggering an exception in the aspnet-request pattern converter, which causes the entire log event to be discarded. This impacts the integrity of logging and could hinder forensic or auditing efforts. There is no direct confidentiality or availability impact reported.
Mitigation Recommendations
Users are recommended to upgrade Apache log4net to version 3.5.0 or later, where this issue is fixed. No other mitigations are specified.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- UBUNTU-CVE-2026-105242
- Osv Schema Version
- 1.7.0
- Ecosystems
- ["Ubuntu:16.04:LTS","Ubuntu:18.04:LTS","Ubuntu:20.04:LTS","Ubuntu:22.04:LTS","Ubuntu:24.04:LTS","Ubuntu:26.10","Ubuntu:26.04:LTS"]
- Cvss Version
- 3.1
- State
- PUBLISHED
Threat ID: 6ad3f4f22cdf04f6566575e2
Added to database: 10/17/2026, 22:21:38 UTC
Last enriched: 10/17/2026, 22:40:15 UTC
Last updated: 10/17/2026, 22:40:15 UTC
Views: 2
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