Vulnerability Description
lichess.org is the forever free, adless and open source chess server. Any approved streamer can inject arbitrary HTML into /streamer and the homepage “Live streams” widget by placing markup in their Twitch/YouTube stream title. CSP is present and blocks inline script execution, but the issue is still a server-side HTML injection sink. To trigger this, a Lichess account only needs to satisfy the normal streamer requirements and get approved. Per Streamer.canApply, that means an account older than 2 days with at least 15 games, or a verified/titled account. After moderator approval, once the streamer goes live, Lichess pulls the platform title and renders it into the UI as-is. No extra privileges are needed beyond a normal approved streamer profile. This vulnerability is fixed with commit 0d5002696ae705e1888bf77de107c73de57bb1b3.
CVSS Score
MEDIUM
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Lichess | Lila | < 2026-03-31 |
Related Weaknesses (CWE)
References
- https://github.com/lichess-org/lila/commit/0d5002696ae705e1888bf77de107c73de57bbPatch
- https://github.com/lichess-org/lila/security/advisories/GHSA-v7gh-939r-pfjqExploitVendor Advisory
- https://vimeo.com/1175908262Exploit
FAQ
What is CVE-2026-35208?
CVE-2026-35208 is a vulnerability with a CVSS score of 5.4 (MEDIUM). lichess.org is the forever free, adless and open source chess server. Any approved streamer can inject arbitrary HTML into /streamer and the homepage “Live streams” widget by placing markup in their T...
How severe is CVE-2026-35208?
CVE-2026-35208 has been rated MEDIUM with a CVSS base score of 5.4/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-35208?
Check the references section above for vendor advisories and patch information. Affected products include: Lichess Lila.