Background

The module controller in SimpleSAML\Module that processes requests for pages
hosted by modules, has code to identify paths ending with .php and process
those as PHP code. If no other suitable way of handling the given path exists it
presents the file to the browser.

Description

The check to identify paths ending with .php does not account for uppercase
letters. If someone requests a path ending with e.g. .PHP and the server is
serving the code from a case-insensitive file system, such as on Windows, the
processing of the PHP code does not occur, and the source code is instead
presented to the browser.

Affected versions

SimpleSAMLphp versions 1.18.5 and older.

Impact

An attacker may use this issue to gain access to the source code in third-party
modules that is meant to be private, or even sensitive. However, the attack
surface is considered small, as the attack will only work when SimpleSAMLphp
serves such content from a file system that is not case-sensitive, such as on
Windows.

Resolution

Upgrade the SimpleSAMLphp installation to version 1.18.6.

Credit

This vulnerability was discovered and reported by Sławek Naczyński.