Insufficient Logging Affecting log4net package, versions [,3.5.0)
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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- published7 Oct 2026
- disclosed6 Oct 2026
- creditUnknown
Introduced: 6 Oct 2026
NewCVE-2026-105243 (opens in a new tab)How to fix?
Upgrade log4net to version 3.5.0 or higher.
Overview
Affected versions of this package are vulnerable to Insufficient Logging in EventLogAppender, which truncates a rendered event to a fixed 31837 characters while the Windows Event Log applies a whole record budget that the log name, source, and machine name are also spent from, so the ceiling it enforces sits above the real one. An attacker can suppress an event record entirely rather than have it shortened, since the service stores nothing and reports nothing once the budget is exceeded, by sending content that drives the rendered message past the real limit. This affects Windows applications using EventLogAppender, and the margin available to an attacker narrows further where ApplicationName is long, since it defaults to the app domain name.