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Vulnerability · Published Oct 22, 2026 · Assigned by GitHub_M

CVE-2026-54238Supabase Realtime: Expired JWTs with string exp are accepted by REST broadcast authorization

Low 3.1

In plain English

A low-severity security flaw in realtime from supabase. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 11% of all known vulnerabilities).

Severity (CVSS 3.1)3.1Low
Exploit odds (30 days)0.2%top 89.2% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official 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.

Affected products (as reported)

VendorProductVersions
supabase realtime < 2.103.1

Weakness: CWE-613 · Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N

References