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  4. CVE 2026 105241 apache log4net unencodable content discards a
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Back to active CVEs
Medium · CVSS 5.3CVE-2026-105241

Apache log4net: Unencodable content discards a whole SmtpPickupDirAppender batchCVE-2026-105241

Answer in brief

CVE-2026-105241 records a Medium severity (CVSS 5.3) vulnerability in Apache log4net: Unencodable content discards a whole SmtpPickupDirAppender batch. The current sources do not mark it as known exploited. The current feed maps Apache Software Foundation/log4net (generic), Apache Software Foundation/log4net (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Oct 6, 2026Updated Oct 6, 2026Source checked Oct 7, 2026First seen by HOL Oct 6, 2026Material review Oct 6, 2026
Upstream Advisory

Key facts

Risk
Medium · CVSS 5.3
Exploitation
Not marked as known exploited
Affected software
2 mapped packages or products
Fix availability
Available

Why this deserves its current priority

CVSS is 5.3. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps Apache Software Foundation/log4net (generic), Apache Software Foundation/log4net (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
PackageAffected rangeFixed version
Apache Software Foundation/log4netgeneric>=1.2.9 <3.5.03.5.0
Apache Software Foundation/log4netgeneric>=02e1e115435888485f2e28b414d267e39e799e07 <4d2e10f0908199604b4326f9df6d0b43b871e3334d2e10f0908199604b4326f9df6d0b43b871e333

Recommended response

  1. 1Check inventory. Check lockfiles and deployed manifests for Apache Software Foundation/log4net, Apache Software Foundation/log4net.
  2. 2Review the reported fix. Update Apache Software Foundation/log4net to 3.5.0; Apache Software Foundation/log4net to 4d2e10f0908199604b4326f9df6d0b43b871e333 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

  1. Published upstream

    Oct 6, 2026

    Evidence: source:cvelist:source_dates:source-dates:record

  2. Source modified

    Oct 6, 2026

    Evidence: source:cvelist:source_dates:source-dates:record

  3. First seen by HOL

    Oct 6, 2026

Sources and claim methodology

  • GitHub security advisorygithub.com
  • GitHub security advisorygithub.com
  • Source referencelists.apache.org
Upstream source description

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.

Quoted source text, attributed separately from HOL analysis.

Related CVEs

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  • Langflow OSS is affected by multiple vulnerabilitiesSame generic ecosystem
  • Langflow OSS is affected by multiple vulnerabilitiesSame generic ecosystem
  • Langflow OSS is affected by multiple vulnerabilitiesSame generic ecosystem

Record context

Vulnerability class
Vulnerability
EPSS
Not reported
CWE IDs
CWE-176
Source
CVE List V5
Source checked
Oct 7, 2026
References
3 linked sources
Open source record