CVE WatchOct 9, 2026

CVE-2026-105241

Improper Handling of Unicode Encoding vulnerability in the SmtpPickupDirAppender of Apache log4net. Content that the mail file writer canno

CVSS

5.3

Medium

EPSS

0.8%

p57

KEV

—

Exploit Today

0-100

Published: Oct 6, 2026 · Last modified: Oct 9, 2026 · CWE-176

EPSS · 30d

0.3%EPSS · 30 days0.8%

2026-10-072026-10-19

Technical 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.

Official references

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