A flaw was found in the PathResourceManager component of the Undertow web server. This component is responsible for serving static files from the file system. The issue occurs because the mechanism used to verify if a symbolic link points to a safe location only checks if the target path starts with a specific string, without ensuring it matches a full directory name. This could allow an attacker to access files in a sibling directory if that directorys name starts with the same characters as an authorized safe directory.

A flaw was found in the PathResourceManager component of the Undertow web server. This component is responsible for serving static files from the file system. The issue occurs because the mechanism used to verify if a symbolic link points to a safe location only checks if the target path starts with a specific string, without ensuring it matches a full directory name. This could allow an attacker to access files in a sibling directory if that directorys name starts with the same characters as an authorized safe directory.

Affected: Ubuntu:Pro:16.04:LTS: undertow, Ubuntu:Pro:18.04:LTS: undertow, Ubuntu:Pro:20.04:LTS: undertow, Ubuntu:Pro:22.04:LTS: undertow, Ubuntu:Pro:24.04:LTS: undertow, Ubuntu:26.10: undertow, Ubuntu:26.04:LTS: undertow

(A flaw was found in the PathResourceManager component of the Undertow ...)