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CVE-2025-27794
No affected components available
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.
The vulnerability can be exploited over the network without needing physical access. It is difficult for an attacker to exploit this vulnerability and may require special conditions. An attacker does not need any special privileges or access rights. The attacker needs the user to perform some action, like clicking a link. The impact is confined to the system where the vulnerability exists. There is a high impact on the confidentiality of the information. There is a high impact on the integrity of the data.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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