Disclosure summary
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.
Source-reported weakness categories
CWE-158
Source-specific records & product guidance
Sources retain their own attribution and scoring. Follow the original record to confirm affected versions, fixed releases, and configuration conditions.
NIST National Vulnerability Database · NVD-CVE-2026-105239
Open original source · Updated Oct 09, 2026
Only CPE matches marked vulnerable=true are indexed. AND/OR platform conditions must be checked in the original NVD record.
| Vendor | Product / association | Version / bounds |
|---|---|---|
| apache | log4net | * {"versionStartIncluding":"1.2.9","versionEndExcluding":"3.5.0"} |
Original records & references
- NIST NVD record
- CVE Program record
- github.com — Patch
- github.com — Patch
- lists.apache.org — Mailing List, Vendor Advisory
PUBLISHED 2026-10-06T16:17:15-04:00
MODIFIED 2026-10-09T11:44:02-04:00
INGESTED 2026-10-10T20:50:46-04:00