CVE-2026-105243

Name of the Vulnerable Software and Affected Versions Apache log4net versions 1.2.9 through 3.4.x

Description Insufficient logging occurs in the EventLogAppender on Windows. Long messages are truncated to a fixed size that, when combined with log and source names, exceeds the Windows Event Log capacity. This causes the event log to store and report nothing, allowing a party capable of influencing log message data to suppress the entire record by increasing its length.

Recommendations Upgrade to version 3.5.0.