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GHSA-cvrm-5hp6-h523
No affected components available
Summary
The logout endpoint accepts a url query parameter to redirect to. casserver treats that url as trusted, and either (depending on configuration) redirects the browser there, or shows a "you've been logged out" page with a link to continue to that url.
There are a number of other things broken with logout in 7 (cas v3 uses a different query parameters, etc)
Details
https://github.com/simplesamlphp/simplesamlphp-module-casserver/blob/21418f7efbea8c4f078fd4a7d1b9eacf94dd4941/src/Controller/LogoutController.php#L104
Previous module checked the url against the valid service urls.
PoC
The docker instructions from the README.md run an image with a vulnerable config.
Accessing https://localhost/cas/logout?url=https://google.com will redirect to Google
Impact
Impacted configs have
'enable_logout' => true,
and are most impacted if they also have
'skip_logout_page' -> true,
The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. The attacker needs the user to perform some action, like clicking a link. The vulnerability can affect other systems as well, not just the initial system. There is a low impact on the integrity of the data.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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