CVE-2026-104721

A flaw was found in logback-classic. This path traversal vulnerability allows a remote attacker to create and append log files outside the intended directory. The issue occurs when an unsanitized Mapped Diagnostic Context (MDC) discriminator value flows into a nested log file path, enabling an attacker who can influence this context, such as through an HTTP request header, to manipulate the destination file location.

This flaw has a Moderate impact because applications using logback-classic may allow a remote attacker who controls an MDC value, such as through an HTTP header, to create or append log files outside the intended directory when that value is used in a nested FileAppender path.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.