SB2025031285 - Session Fixation in Flarum

Description

This security bulletin contains information about 1 security vulnerability.

1) Session Fixation (CVE-ID: CVE-2025-27794)

The vulnerability allows a remote attacker to hijack a user's session.

The vulnerability exists due to improper session management in session token handling when an attacker-controlled authoritative subdomain sets cookies scoped to the parent domain. A remote attacker can set a crafted cookie containing the attacker's session token to hijack a user's session.

User interaction is required, and exploitation is possible only when the parent domain is not on the Public Suffix List and the attacker controls a direct child subdomain.

Remediation

Install update from vendor's website.

References

• https://github.com/flarum/framework/security/advisories/GHSA-hg9j-64wp-m9px
• https://github.com/advisories/GHSA-hg9j-64wp-m9px