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.
Attack Parameters
Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Privileges Required
None
No privileges needed
User Interaction
None
No user interaction needed
Impact Assessment
Confidentiality
None
No data leak
Integrity
Low
Partial data modification
Availability
None
No disruption
CVSS Vector v3.1
Weakness Type (CWE)
Vulnerable Products 1
| Configuration | From (including) | Up to (excluding) |
|---|---|---|
|
Apache Log4net
cpe:2.3:a:apache:log4net:*:*:*:*:*:*:*:*
|
1.2.11
|
3.5.0
|
References 4
https://github.com/apache/logging-log4net/commit/145203420c579a703008b4b723b6a0…
security@apache.org
https://github.com/apache/logging-log4net/pull/316
security@apache.org
https://lists.apache.org/thread.html/zg6dbqm4ztm7j3c21nfsqj0yxm5yrpdx
security@apache.org
http://www.openwall.com/lists/oss-security/2026/10/07/16
af854a3a-2127-422b-91ae-364da2661108