Improper Encoding or Escaping of Output 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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Test your applications- Snyk IDSNYK-DOTNET-LOG4NET-20550530
- published7 Oct 2026
- disclosed6 Oct 2026
- creditUnknown
Introduced: 6 Oct 2026
NewCVE-2026-105244 (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 Improper Encoding or Escaping of Output in RemoteSyslogAppender.AppendMessage(), which drops every character outside the visible ASCII range and space that RFC 3164 permits, rather than representing it, so non-Latin text and control characters such as tab are removed from the record with no marker left behind. An attacker can make distinct values appear identical in the collected logs, such as a username containing a zero width space arriving as admin, by placing characters outside that range into content that is logged. This affects only applications using RemoteSyslogAppender, and requires the attacker to control data that reaches a logged message.