Path-traversal vulnerability in QOS.CH Sarl Logback-classic on Java (logback-classic module) allows path-traversal vulnerability. More specifically, an MDC-based discriminator value flows unsanitized into a nested FileAppender path, letting an attacker who influences that MDC value (e.g. via an HTTP header) create and append log files outside the intended directory. This issue affects Logback-classic: from 0.9.14 through 1.6.4.  This vulnerability is similar to CVE-2026-19880 but involves other attack techniques.