All vulnerabilities
CVE-2026-105242

Apache log4net: Request validation failure drops the event in the aspnet-request converter

Apache Software Foundation Apache log4net
Open in ThreatlineRecord JSON
CVSS
5.3Medium
ExploitationNo known exploitationNot in CISA KEV, which does not prove it is unexploitedCISA KEV
Exploit odds (EPSS)0.82%Chance of exploitation activity in the next 30 days, higher than 56% of CVEs. Scored 23 Oct 2026FIRST EPSS
Fixed in3.5.0Also 145203420c579a703008b4b723b6a080757f4964CVE List
Published6 Oct 2026Updated 7 Oct 2026CVE List

What fixes it

  • 3.5.0Apache log4netCVE List
  • 145203420c579a703008b4b723b6a080757f4964Apache log4netCVE List

A fixed version on one release line is not the upgrade target for every line. Check your exact version and any vendor backports.

Description

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.

Text from CVE List

Affected versions 2

  • Apache log4netaffected: 1.2.11 before 3.5.0CVE List
  • Apache log4netaffected: 243f1e9f3ee235955bade4b4fe664a903378719a before 145203420c579a703008b4b723b6a080757f4964CVE List

References 3