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.
History

Fri, 30 Oct 2026 16:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Fri, 23 Oct 2026 00:45:00 +0000

Type Values Removed Values Added
First Time appeared Supabase
Supabase realtime
Vendors & Products Supabase
Supabase realtime

Thu, 22 Oct 2026 17:45:00 +0000

Type Values Removed Values Added
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.
Title Supabase Realtime: Expired JWTs with string exp are accepted by REST broadcast authorization
Weaknesses CWE-613
References
Metrics cvssV3_1

{'score': 3.1, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N'}


cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published: 2026-10-22T17:22:50.862Z

Updated: 2026-10-30T15:11:34.608Z

Reserved: 2026-06-12T16:25:43.084Z

Link: CVE-2026-54238

cve-icon Vulnrichment

Updated: 2026-10-30T15:11:29.226Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-10-22T18:17:28.993

Modified: 2026-10-30T16:17:56.533

Link: CVE-2026-54238

cve-icon Redhat

No data.