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Vulnerability record · CVE-2025-27794 · published 12 March 2025

CVE-2025-27794: Flarum injection vulnerability

Flarum · Flarum

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.

6.8 CVSS 3.1 Medium EPSS 0.49% · top 60.2% CWE-74 · Injection
6.8CVSS 3.1 base score
0.49%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
3References
17 Jun 2026Last modified by NVD

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:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/flarum/framework/commit/a05aaea3ee1e0a8b870935183193cd6052f1d402 Patch
https://github.com/flarum/framework/releases/tag/v1.8.10 Release Notes
https://github.com/flarum/framework/security/advisories/GHSA-hg9j-64wp-m9px Vendor Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2025-27794), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.