Apache log4net: Unencodable content discards a whole SmtpPickupDirAppender batch

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-105241
StatePUBLISHED
Assignerapache
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-06 20:17:15 UTC
Updated2026-10-06 20:17:15 UTC
DescriptionImproper 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.

Risk And Classification

Primary CVSS: v3.1 5.3 MEDIUM from [email protected]

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Problem Types: CWE-176 | CWE-176 CWE-176 Improper Handling of Unicode Encoding

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary5.3MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
3.1CNACVSS5.3MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Apache Software Foundation Apache Log4net affected 1.2.9 3.5.0 semver Not specified
CNA Apache Software Foundation Apache Log4net affected 02e1e115435888485f2e28b414d267e39e799e07 4d2e10f0908199604b4326f9df6d0b43b871e333 git Not specified

References

ReferenceSourceLinkTags
lists.apache.org/thread.html/hg8dgh3oy8bp3dhb8nsygk9kw2o401ws [email protected] lists.apache.org
github.com/apache/logging-log4net/pull/315 [email protected] github.com
github.com/apache/logging-log4net/commit/4d2e10f0908199604b4326f9df6d0b4... [email protected] github.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: The Apache Software Foundation (en)

CNA: Claude Security (en)

CNA: Jan Friedrich (en)

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