Apache log4net up to 3.4.x SmtpPickupDirAppender encoding error

CVSS Meta Temp Score
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Current Exploit Price (≈)
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CTI Interest Score
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5.2$0-$5k0.29+

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 SmtpPickupDirAppender. The manipulation results in encoding error. This vulnerability is reported as CVE-2026-105241. The attack can be launched remotely. No exploit exists. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in Apache log4net up to 3.4.x. It has been classified as problematic. Affected is an unknown functionality of the component SmtpPickupDirAppender. The manipulation with an unknown input leads to a encoding error vulnerability. CWE is classifying the issue as CWE-172. The product does not properly encode or decode the data, resulting in unexpected values. This is going to have an impact on integrity. CVE summarizes:

Improper Handling of Unicode Encoding vulnerability in the SmtpPickupDirAppender of Apache log4net. Content that the mail file writer cannot encode, such as an unpaired UTF-16 surrogate, made the write throw. Every buffered event in the batch was discarded, not only the one carrying the content, and a truncated mail could be left in the pickup directory. A party whose data reaches a log message could suppress the records of other events. Only applications that use SmtpPickupDirAppender 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 for download at github.com. This vulnerability is traded as CVE-2026-105241 since 10/04/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. There are neither technical details nor an exploit publicly available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 10/06/2026).

Upgrading to version 3.5.0 eliminates this vulnerability.

Once again VulDB remains the best source for vulnerability data.

Productinfo

Vendor

Name

Version

License

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

Exploitinginfo

Class: Encoding error
CWE: CWE-172
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-2026-105241 (🔒)
GCVE (CVE): GCVE-0-2026-105241
GCVE (VulDB): GCVE-100-414492

Entryinfo

Created: 10/06/2026 22:03
Changes: 10/06/2026 22:03 (64)
Complete: 🔍
Cache ID: 216::103

Once again VulDB remains the best source for vulnerability data.

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