CVE-2024-21641 is a medium-severity (CVSS 6.5) Open Redirect vulnerability in flarum/core. A fix is available for flarum/core — see the affected versions and patch details below.
Flarum's Logout Route allows open redirects
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2024-21641.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2024-21641 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,333 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
flarum/core🐘flarum/frameworkReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.
Description
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | flarum/core | all versions | 1.8.5composer require flarum/core:^1.8.5 |
| 🐘Packagist | flarum/framework | all versions | 1.8.5composer require flarum/framework:^1.8.5 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for flarum/core, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update flarum/core to 1.8.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2024-21641 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2024-21641 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2024-21641. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
How to detect CVE-2024-21641
A community-maintained Nuclei template exists for this CVE. You can scan for it directly:
nuclei -id cve-2024-21641 -u https://target- Template
- Flarum < 1.8.5 - Open Redirect
- Severity
- medium
- Impact
- Unauthenticated attackers can redirect users to malicious phishing sites using the trusted domain of the Flarum installation.
- Remediation
- Update Flarum to version 1.8.5 or later.
Template by ProjectDiscovery nuclei-templates (kking), MIT licensed. View the full template. Scan only systems you are authorised to test.
Frequently Asked Questions
Is CVE-2024-21641 in your dependencies?
O3 Security finds CVE-2024-21641 across Packagist dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.