How severe is CVE-2026-105241?

CVE-2026-105241 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity low, and availability none.

Is CVE-2026-105241 being actively exploited?

It is not currently listed in CISA's Known Exploited Vulnerabilities catalog, and no EPSS exploit-prediction score is available yet.

How do I fix CVE-2026-105241?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2026-105241 published?

CVE-2026-105241 was published on 2026-10-06.

CVE-2026-105241

CVE-2026-105241 is a medium-severity vulnerability with a CVSS 3.x base score of 5.3. The underlying weakness is classified as CWE-176.

Key facts

Severity: Medium (CVSS 3.x base score 5.3)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-176
Published: 2026-10-06
Last modified: 2026-10-06

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.

Frequently asked questions

What is CVE-2026-105241?: 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.
How severe is CVE-2026-105241?: CVE-2026-105241 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity low, and availability none.
Is CVE-2026-105241 being actively exploited?: It is not currently listed in CISA's Known Exploited Vulnerabilities catalog, and no EPSS exploit-prediction score is available yet.
How do I fix CVE-2026-105241?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2026-105241 published?: CVE-2026-105241 was published on 2026-10-06.

References

Other CWE-176 vulnerabilities

CVE-2025-71316 — Critical (CVSS 9.8): SQLite 'sqldiff.exe' does not securely handle the way the Microsoft Windows C runtime converts Unicode characters to…
CVE-2024-24691 — Critical (CVSS 9.6): Improper input validation in Zoom Desktop Client for Windows, Zoom VDI Client for Windows, and Zoom Meeting SDK for…
CVE-2026-23950 — High (CVSS 8.8): node-tar,a Tar for Node.js, has a race condition vulnerability in versions up to and including 7.5.3. This is due to an…
CVE-2026-93990 — High (CVSS 7.5): Expat before 2.8.5 fails to validate that a high surrogate in UTF-16 input is followed by a low surrogate, allowing…
CVE-2024-43093 — High (CVSS 7.3): In shouldHideDocument of ExternalStorageProvider.java, there is a possible bypass of a file path filter designed to…
CVE-2026-4116 — High (CVSS 7.2): Improper handling of Unicode encoding in SonicWall SMA1000 series appliances allows a remote authenticated SSLVPN user…

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