CVE-2025-27794: medium-severity vulnerability in flarum framework
Flarum Vulnerable to Session Hijacking via Authoritative Subdomain Cookie Overwrite
Published
13Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 6.8epss 0.5%
exploitation probability
0.5%top 57% of all CVEs
observed exploitation
nono source reports it
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:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N
Affected products
flarum · frameworkRelated CVEs — flarum framework
In the same product, most dangerous first.
CVE-2024-21641MEDIUMFlarum's Logout Route allows open redirectsEPSS 1.1%CVE-2023-27577MEDIUMPath Traversal Vulnerability in `LESS` Parser allows reading of sensitive server files in flarumEPSS 0.9%CVE-2022-41938CRITICALCross site scripting vulnerability with discussion titles in flarumEPSS 0.8%CVE-2023-22487HIGHPost mentions can be used to read any post on the forum without access controlEPSS 0.7%CVE-2023-22489LOWFlarum is missing authorization in discussion repliesEPSS 0.6%CVE-2023-40033HIGHServer-Side Request Forgery via Avatar upload in flarumEPSS 0.5%