Vulnerability Description
AuthRestServlet in Matrix Synapse before 1.21.0 is vulnerable to XSS due to unsafe interpolation of the session GET parameter. This allows a remote attacker to execute an XSS attack on the domain Synapse is hosted on, by supplying the victim user with a malicious URL to the /_matrix/client/r0/auth/*/fallback/web or /_matrix/client/unstable/auth/*/fallback/web Synapse endpoints.
CVSS Score
MEDIUM
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Matrix | Synapse | < 1.21.0 |
Related Weaknesses (CWE)
References
- https://github.com/matrix-org/synapse/pull/8444Issue TrackingPatchThird Party Advisory
- https://github.com/matrix-org/synapse/releases/tag/v1.21.2Release NotesThird Party Advisory
- https://github.com/matrix-org/synapse/security/advisories/GHSA-3x8c-fmpc-5rmqPatchThird Party Advisory
- https://matrix.org/blog/2020/10/15/synapse-1-21-2-released-and-security-advisoryRelease NotesVendor Advisory
- https://github.com/matrix-org/synapse/pull/8444Issue TrackingPatchThird Party Advisory
- https://github.com/matrix-org/synapse/releases/tag/v1.21.2Release NotesThird Party Advisory
- https://github.com/matrix-org/synapse/security/advisories/GHSA-3x8c-fmpc-5rmqPatchThird Party Advisory
- https://matrix.org/blog/2020/10/15/synapse-1-21-2-released-and-security-advisoryRelease NotesVendor Advisory
FAQ
What is CVE-2020-26891?
CVE-2020-26891 is a vulnerability with a CVSS score of 6.1 (MEDIUM). AuthRestServlet in Matrix Synapse before 1.21.0 is vulnerable to XSS due to unsafe interpolation of the session GET parameter. This allows a remote attacker to execute an XSS attack on the domain Syna...
How severe is CVE-2020-26891?
CVE-2020-26891 has been rated MEDIUM with a CVSS base score of 6.1/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2020-26891?
Check the references section above for vendor advisories and patch information. Affected products include: Matrix Synapse.