CVE-2026-105240
Published:October 06, 2026
Updated:October 10, 2026
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.
Affected Packages
log4net (DOT_NET):
Affected version(s) >=3.0.0.0 <3.5.0Fix Suggestion:
Update to version 3.5.0https://github.com/apache/logging-log4net.git (GITHUB):
Affected version(s) >=rel/3.0.0 <rel/3.5.0Fix Suggestion:
Update to version rel/3.5.0log4net (NUGET):
Affected version(s) >=3.0.0 <3.5.0Fix Suggestion:
Update to version 3.5.0Related Resources (8)
Do you need more information?
Contact UsCVSS v4
Base Score:
6.9
Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
NONE
Privileges Required
NONE
User Interaction
NONE
Vulnerable System Confidentiality
NONE
Vulnerable System Integrity
LOW
Vulnerable System Availability
NONE
Subsequent System Confidentiality
NONE
Subsequent System Integrity
NONE
Subsequent System Availability
NONE
CVSS v3
Base Score:
5.3
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
LOW
Availability
NONE
Weakness Type (CWE)
Improper Neutralization of Null Byte or NUL Character
EPSS
Base Score:
0.33