Apache log4net up to 3.4.x EventLogAppender neutralization

CVSS Meta Temp Score
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CTI Interest Score
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5.2$0-$5k0.88+

Summaryinfo

A vulnerability classified as problematic has been found in Apache log4net up to 3.4.x. The affected element is an unknown function of the component EventLogAppender. The manipulation leads to neutralization. This vulnerability is uniquely identified as CVE-2026-105239. The attack is possible to be carried out remotely. No exploit exists. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as problematic, has been found in Apache log4net up to 3.4.x. This issue affects some unknown processing of the component EventLogAppender. The manipulation with an unknown input leads to a neutralization vulnerability. Using CWE to declare the problem leads to CWE-707. The product does not ensure or incorrectly ensures that structured messages or data are well-formed and that certain security properties are met before being read from an upstream component or sent to a downstream component. Impacted is integrity. The summary by CVE is:

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.

The advisory is shared at github.com. The identification of this vulnerability is CVE-2026-105239 since 10/04/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Neither technical details nor an exploit are publicly available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 10/06/2026).

Upgrading to version 3.5.0 eliminates this vulnerability.

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

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Version

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CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 5.3
VulDB Meta Temp Score: 5.2

VulDB Base Score: 5.3
VulDB Temp Score: 5.1
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 5.3
CNA Vector (apache): 🔒

CVSSv2info

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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Neutralization
CWE: CWE-707 / CWE-20
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined
Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: log4net 3.5.0

Timelineinfo

10/04/2026 CVE reserved
10/06/2026 +2 days Advisory disclosed
10/06/2026 +0 days VulDB entry created
10/06/2026 +0 days VulDB entry last update

Sourcesinfo

Vendor: apache.org

Advisory: github.com
Status: Confirmed

CVE: CVE-2026-105239 (🔒)
GCVE (CVE): GCVE-0-2026-105239
GCVE (VulDB): GCVE-100-414497

Entryinfo

Created: 10/06/2026 22:05
Changes: 10/06/2026 22:05 (64)
Complete: 🔍
Cache ID: 216::103

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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