Vulnerability Description
Flarum is open-source forum software. A session hijacking vulnerability exists in versions prior to 1.8.10 when an attacker-controlled authoritative subdomain under a parent domain (e.g., `subdomain.host.com`) sets cookies scoped to the parent domain (`.host.com`). This allows session token replacement for applications hosted on sibling subdomains (e.g., `community.host.com`) if session tokens aren't rotated post-authentication. Key Constraints are that the attacker must control any subdomain under the parent domain (e.g., `evil.host.com` or `x.y.host.com`), and the parent domain must not be on the Public Suffix List. Due to non-existent session token rotation after authenticating we can theoretically reproduce the vulnerability by using browser dev tools, but due to the browser's security measures this does not seem to be exploitable as described. Version 1.8.10 contains a patch for the issue.
CVSS Score
MEDIUM
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Flarum | Flarum | < 1.8.0 |
Related Weaknesses (CWE)
References
- https://github.com/flarum/framework/commit/a05aaea3ee1e0a8b870935183193cd6052f1dPatch
- https://github.com/flarum/framework/releases/tag/v1.8.10Release Notes
- https://github.com/flarum/framework/security/advisories/GHSA-hg9j-64wp-m9pxVendor Advisory
FAQ
What is CVE-2025-27794?
CVE-2025-27794 is a vulnerability with a CVSS score of 6.8 (MEDIUM). Flarum is open-source forum software. A session hijacking vulnerability exists in versions prior to 1.8.10 when an attacker-controlled authoritative subdomain under a parent domain (e.g., `subdomain.h...
How severe is CVE-2025-27794?
CVE-2025-27794 has been rated MEDIUM with a CVSS base score of 6.8/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2025-27794?
Check the references section above for vendor advisories and patch information. Affected products include: Flarum Flarum.