CVE-2026-54238

Supabase Realtime: Expired JWTs with string exp are accepted by REST broadcast authorization

Published Oct 22, 2026 CVSS 3.1 · 3.1 Low EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
Metrics ssvc

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

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

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Oct 30, 2026, 3:11 PM
Reserved
Jun 12, 2026, 4:25 PM
Status
Awaiting Analysis
Published
Oct 22, 2026, 6:17 PM
Modified
Oct 30, 2026, 4:17 PM