CVE-2026-105239
Received
Received - Intake
Null Byte Injection in Apache log4net EventLogAppender
Vulnerability report for CVE-2026-105239, including description, CVSS score, EPSS score, affected products, exploitability, helpful resources, and attack-flow context.
Publication date: 2026-10-06
Last updated on: 2026-10-06
Assigner: Apache Software Foundation
Description
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.
CVSS Scores
EPSS Scores
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| Percentile: |
Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| Apache | Software | Foundation Apache log4net 1.2.9 |
| Apache | Software | Foundation Apache log4net 02e1e115435888485f2e28b414d267e39e799e07 |
Helpful Resources
Exploitability
CWE
KEV
| CWE ID | Description |
|---|---|
| CWE-158 | The product receives input from an upstream component, but it does not neutralize or incorrectly neutralizes NUL characters or null bytes when they are sent to a downstream component. |
