CVE-2026-105241Apache log4net: Unencodable content discards a whole SmtpPickupDirAppender batch
Updated under an hour ago ()
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It affects Apache Software Foundation Apache log4net and 1 other product. Add what you run to find out whether that includes you.
No exploitation reported and no EPSS estimate yet.
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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
- 5.3 MEDIUM (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
- Weakness (CWE)
- CWE-176
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- apache
- NVD analysis
- Analyzed
- Record last updated
- Oct 7, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
Apache Software Foundation Apache log4net apache_software_foundation:apache_log4net (from the name) | from 1.2.9 before 3.5.0 | CNA record |
apache log4net apache:log4net | from 1.2.9 before 3.5.0 | NVD |
References
- https://github.com/apache/logging-log4net/pull/315patch
- https://github.com/apache/logging-log4net/commit/4d2e10f0908199604b4326f9df6d0b43b871e333patch
- https://lists.apache.org/thread.html/hg8dgh3oy8bp3dhb8nsygk9kw2o401wsvendor-advisory, mailing-list
- http://www.openwall.com/lists/oss-security/2026/10/07/15mailing-list, third-party-advisory
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.