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CVE-2026-105243

Apache log4net: Oversize EventLogAppender record silently discarded

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 3.5.0
None on Exploit-DB, Metasploit or GitHub
  • Exploitation: none
  • Automatable: yes
  • Technical impact: partial

Summary

Insufficient Logging vulnerability in the EventLogAppender of Apache log4net. Long messages were truncated to a fixed size that exceeds what the Windows Event Log accepts once the log and source names are counted, and the event log then stored nothing and reported nothing. A party whose data reaches a log message could suppress the whole record by making it long enough. Only applications on Windows that use EventLogAppender 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.

Timeline

  1. CVE published
  2. CISA SSVC assessment

    Exploitation: none · Automatable: yes · Technical impact: partial

  3. Record last updated

Affected versions

  • log4net

    From 1.2.9 · fixed in 3.5.0

  • log4net

    From 02e1e115435888485f2e28b414d267e39e799e07 · fixed in 28fbfb25678c48a8cc5bc9b94ead0dddfc39ffed

References 3

GitHub · apache/logging-log4net

lists.apache.org