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

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-54238
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-22 18:17:28 UTC
Updated2026-10-22 18:17:28 UTC
DescriptionSupabase 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.

Risk And Classification

Primary CVSS: v3.1 3.1 LOW from [email protected]

CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N

Problem Types: CWE-613 | CWE-613 CWE-613: Insufficient Session Expiration

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary3.1LOWCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N
3.1CNADECLARED3.1LOWCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
High
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Supabase Realtime affected < 2.103.1 Not specified

References

ReferenceSourceLinkTags
github.com/supabase/realtime/commit/ac229d7eff2798b12b994e07bdd64f5e9b56... [email protected] github.com
github.com/supabase/realtime/pull/1934 [email protected] github.com
github.com/supabase/realtime/releases/tag/v2.103.1 [email protected] github.com
github.com/supabase/realtime/security/advisories/GHSA-hg9h-6mhq-6c2v [email protected] github.com
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