Improper Neutralization of Null Byte or NUL Character vulnerability in the OutputDebugStringAppender of Apache log4net. A NUL character in logged content ended the debug output record at that point, so everything the layout rendered after it, including exception text and trailing fields, was silently lost. A party whose data reaches a log message could hide the rest of that record.
Only applications on Windows that use OutputDebugStringAppender 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/6046fe9d7f353b49fe995361c071ec…
security@apache.org
https://github.com/apache/logging-log4net/pull/315
security@apache.org
https://lists.apache.org/thread.html/gyw2d4ppy82t1vlpdknkfd1nmzp21z17
security@apache.org
http://www.openwall.com/lists/oss-security/2026/10/07/18
af854a3a-2127-422b-91ae-364da2661108