How severe is CVE-2024-21641?

CVE-2024-21641 has a CVSS score of 6.5/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2024-21641?

CVE-2024-21641 affects the following packages: flarum/core (Packagist), flarum/framework (Packagist). Ecosystems affected: Packagist.

How do I fix CVE-2024-21641?

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.

How do I detect CVE-2024-21641 in my Packagist dependencies?

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.

How do I mitigate CVE-2024-21641 if there is no patch (or I can't update yet)?

Stop reflecting attacker-controlled destinations: resolve every redirect target against an allowlist of paths or hosts you own, prefer a server-side key over a full URL in the request, and reject absolute URLs entirely where the flow only ever needs a relative one.

Is CVE-2024-21641 actively exploited in the wild?

No public exploit code has been indexed for CVE-2024-21641 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2024-21641?

CVE-2024-21641 has an EPSS (Exploit Prediction Scoring System) score of 1.1%, placing it in the 65th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2024-21641?

CVE-2024-21641 is classified as Open Redirect (CWE-601). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

Is there exploit tooling available for CVE-2024-21641?

A Nuclei detection template exists for CVE-2024-21641, meaning automated scanners can fingerprint it. Public exploit tooling significantly increases real-world risk — prioritize patching and ensure detection coverage. Exploit tooling should only ever be used in isolated, authorized testing environments.

When was CVE-2024-21641 published, and has it been updated?

CVE-2024-21641 was published on January 5, 2024 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐘

🐘 Packagist

Not in CISA KEV

MEDIUM severity

CVE-2024-21641 — core

MEDIUMFix: flarum/flarum-core@ee8b3b4

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

Also known asGHSA-733r-8xcp-w9mr

Published

Jan 5, 2024

Updated

Oct 28, 2026

Affected

2 pkgs

Patched

2 / 2

Exploits

None indexed

Exploitation data as of Nov 5, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

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

via FIRST.org ↗

1.1%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs65th percentile — riskier than 65% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

2 pkgs affected

🐘flarum/core🐘flarum/framework

Real-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

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 [email protected], and we will address it promptly.

Affected Packages

2 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
🐘Packagist	`flarum/core`	all versions	1.8.5`composer require flarum/core:^1.8.5`
🐘Packagist	`flarum/framework`	all versions	1.8.5`composer require flarum/framework:^1.8.5`

Affected Products

1 product · 1 configurations

Application

flarumflarum

< 1.8.5

range

Detection & mitigation playbook

Open-source dependency

Detect
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
Stop reflecting attacker-controlled destinations: resolve every redirect target against an allowlist of paths or hosts you own, prefer a server-side key over a full URL in the request, and reject absolute URLs entirely where the flow only ever needs a relative one.

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

### 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-integrat