Description
Improper Neutralization of Null Byte or NUL Character vulnerability in the EventLogAppender of Apache log4net.
A NUL character in logged content ended the Windows Event Log record at that point, so everything the layout rendered after it, including exception text and trailing fields, was silently not stored. A party whose data reaches a log message could hide the rest of that record. 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.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Apache Software Foundation | Apache log4net | 1.2.9 – < 3.5.0 | 3.5.0 |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | log4net | No fix yet | — |
| Debian 13 | log4net | No fix yet | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.10 | log4net | No fix yet | — |
| Ubuntu 26.04 LTS | log4net | No fix yet | — |
| Ubuntu 24.04 LTS | log4net | No fix yet | — |
| Ubuntu 22.04 LTS | log4net | No fix yet | — |
| Ubuntu 20.04 LTS | log4net | No fix yet | — |
Show 2 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 18.04 LTS | log4net | No fix yet | — |
| Ubuntu 16.04 LTS | log4net | No fix yet | — |
Advisories 1
- WID-SEC-2026-3772 Apache log4net: Mehrere Schwachstellen ermöglichen Manipulation von Dateien BSI CERT-Bund (WID) · Oct 6, 2026