CVE-2024-21641: Flarum's Logout Route allows open redirects
Impact The Flarum /logout route includes a redirect parameter that allows any third party to redirect users from a (trusted) domain of the Flarum installation to redirect to any link. Sample: example.com/logout?return=https://google.com. For logged-in users, the logout must be confirmed. Guests are immediately redirected. This could be used by spammers to redirect to a web address using a trusted domain of a running Flarum installation.
Some ecosystem extensions modifying the logout route have already been affected. Sample: https://discuss.flarum.org/d/22229-premium-wordpress-integration/526
Patches The vulnerability has been fixed and published as flarum/core v1.8.5. All communities running Flarum should upgrade as soon as possible to v1.8.5 using:
composer update --prefer-dist --no-dev -a -W
You can then confirm you run the latest version using:
composer show flarum/core
Workarounds Some extensions modifying the logout route can remedy this issue if their implementation is safe. In any case we recommend updating to 1.8.5.
References For any questions or comments on this vulnerability, please visit https://discuss.flarum.org/
For support questions, create a discussion at https://discuss.flarum.org/t/support.
A reminder that if you ever become aware of a security issue in Flarum, please report it to us privately by emailing security@flarum.org, and we will address it promptly.
Other sources
Flarum is open source discussion platform software. Prior to version 1.8.5, the Flarum /logout route includes a redirect parameter that allows any third party to redirect users from a (trusted) domain of the Flarum installation to redirect to any link. For logged-in users, the logout must be confirmed. Guests are immediately redirected. This could be used by spammers to redirect to a web address using a trusted domain of a running Flarum installation. The vulnerability has been fixed and published as flarum/core v1.8.5. As a workaround, some extensions modifying the logout route can remedy this issue if their implementation is safe.
— NVD
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
composer/flarum/frameworkto a version that resolves this vulnerability.Fixed in 1.8.5 - Upgrade
Upgrade
composer/flarum/coreto a version that resolves this vulnerability.Fixed in 1.8.5 - Upgrade
Upgrade
flarum/coreto a version that resolves this vulnerability.Fixed in 1.8.5 - Configuration
If you cannot upgrade immediately, mitigate the open redirect by ensuring the /logout route’s redirect/return parameter cannot be set to arbitrary external links by untrusted users (e.g., only accept safe/expected post-logout destinations).
Flarum /logout route return redirect parameter = Do not allow third-party control of /logout?return
Event History
Frequently Asked Questions
What is the severity of CVE-2024-21641?
CVE-2024-21641 is considered a medium severity vulnerability due to the potential for open redirects.
How do I fix CVE-2024-21641?
To remediate CVE-2024-21641, upgrade to Flarum version 1.8.5 or later.
What is the impact of CVE-2024-21641?
The impact of CVE-2024-21641 is that it allows unauthorized redirection of users after logout from trusted domains.
Which versions of Flarum are affected by CVE-2024-21641?
Versions of Flarum prior to 1.8.5 are affected by CVE-2024-21641.
What is the nature of the vulnerability in CVE-2024-21641?
CVE-2024-21641 involves an open redirect vulnerability through the logout route which can exploit user trust.