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.
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:*:*:*:*:*:*:*:*
|
1.2.9
|
3.5.0
|
References 4
https://github.com/apache/logging-log4net/commit/28fbfb25678c48a8cc5bc9b94ead0d…
security@apache.org
https://github.com/apache/logging-log4net/pull/315
security@apache.org
https://lists.apache.org/thread.html/jr6fj5skv1vnjbc9jmt8bp151p8ow1rp
security@apache.org
http://www.openwall.com/lists/oss-security/2026/10/07/17
af854a3a-2127-422b-91ae-364da2661108