CVE-2026-105241
mediumImproper Handling of Unicode Encoding vulnerability in the SmtpPickupDirAppender of Apache log4net.
Vendor / product: Apache — log4net
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.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N Affected products
Weakness classification (CWE)
Source: NVD / CISA. “NVD-CWE-Other” and “NVD-CWE-noinfo” mean NVD could not assign a specific weakness.
Mitigation & advisories
References
- https://github.com/apache/logging-log4net/commit/4d2e10f0908199604b4326f9df6d0b43b871e333 security@apache.org
- https://github.com/apache/logging-log4net/pull/315 security@apache.org
- https://lists.apache.org/thread.html/hg8dgh3oy8bp3dhb8nsygk9kw2o401ws security@apache.org
- http://www.openwall.com/lists/oss-security/2026/10/07/15 af854a3a-2127-422b-91ae-364da2661108