CVE-2026-54238: Supabase Realtime: Expired JWTs with string exp are accepted by REST broadcast authorization
Description
Supabase Realtime provides Broadcast, Presence, and Postgres Changes via WebSockets. Prior to version 2.103.1, the REST broadcast endpoints accept an expired JWT when the exp claim is encoded as a JSON string instead of a JSON number. The same route rejects an expired integer exp token signed with the same tenant secret. The accepted request returns 202 and emits the broadcast to subscribers. This could allow an unauthenticated attacker can broadcast realtime messages to subscribers. The attack can be performed via the Internet/only from within the supabase project. The impact of broadcasting messages to subscribers is application specific. This issue has been patched in version 2.103.1.
Vector CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N · CWE-613
Tracked companies
Mapped from the CVE’s affected-product data, NVD CPE matches, vendor advisories or package feeds. A mapping means the vendor’s software is named, not that its hosted service was exposed.
Status incidents that name it
No tracked status incident names this CVE.
Affected vendors and products
supabase: realtime
References
- CVE record on cve.org (opens in new tab)
- NVD entry (opens in new tab)
- github.com/supabase/realtime/commit/ac229d7eff2798b12b994e07bdd64f5e9b56374a (opens in new tab)
- github.com/supabase/realtime/pull/1934 (opens in new tab)
- github.com/supabase/realtime/releases/tag/v2.103.1 (opens in new tab)
- github.com/supabase/realtime/security/advisories/GHSA-hg9h-6mhq-6c2v (opens in new tab)
- CVE records from the CVE Program (cve.org). CVE® is a registered trademark of The MITRE Corporation. (opens in new tab)
- This product uses data from the NVD API but is not endorsed or certified by the NVD. (opens in new tab)
- Known Exploited Vulnerabilities catalog from CISA. (opens in new tab)
- EPSS scores from FIRST (Exploit Prediction Scoring System). (opens in new tab)