Apache log4net up to 3.4.x EventLogAppender insufficient logging

CVSS Meta Temp Score
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CTI Interest Score
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5.2$0-$5k0.31

Summaryinfo

A vulnerability categorized as problematic has been discovered in Apache log4net up to 3.4.x. Affected by this issue is some unknown functionality of the component EventLogAppender. Executing a manipulation can lead to insufficient logging. This vulnerability is handled as CVE-2026-105243. The attack can be executed remotely. There is not any exploit available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in Apache log4net up to 3.4.x. It has been declared as problematic. This vulnerability affects an unknown functionality of the component EventLogAppender. The manipulation with an unknown input leads to a insufficient logging vulnerability. The CWE definition for the vulnerability is CWE-778. When a security-critical event occurs, the product either does not record the event or omits important details about the event when logging it. As an impact it is known to affect integrity. CVE summarizes:

Insufficient Logging vulnerability in the EventLogAppender of Apache log4net. Long messages were truncated to a fixed size that exceeds what the Windows Event Log accepts once the log and source names are counted, and the event log then stored nothing and reported nothing. A party whose data reaches a log message could suppress the whole record by making it long enough. 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 available at github.com. This vulnerability was named CVE-2026-105243 since 10/04/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. The technical details are unknown and an exploit is not available. The structure of the vulnerability defines a possible price range of USD $0-$5k at the moment (estimation calculated on 10/06/2026). This vulnerability is assigned to T1562.002 by the MITRE ATT&CK project.

Upgrading to version 3.5.0 eliminates this vulnerability.

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Productinfo

Vendor

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Version

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Website

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

Exploitinginfo

Class: Insufficient logging
CWE: CWE-778
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-2026-105243 (🔒)
GCVE (CVE): GCVE-0-2026-105243
GCVE (VulDB): GCVE-100-414646

Entryinfo

Created: 10/06/2026 22:56
Changes: 10/06/2026 22:56 (64)
Complete: 🔍
Cache ID: 216::103

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