VulnerabilityAwaiting Analysis

CVE-2026-54238

This could allow an unauthenticated attacker can broadcast realtime messages to subscribers.

LOW 3.1EPSS 0.21%

Does this matter?

Lower severity and a low EPSS score (0.21%). Track it; it rarely justifies an emergency change on its own.

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.

CVSS 3.1: 3.1 LOWCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N
EPSS: 0.21% probability · 11th percentile
Public exploits: None in Exploit-DB
CISA KEV: Not listed
Weakness: CWE-613
Source: security-advisories@github.com

EPSS trend

EPSS moved from 0.2% on 23 October 2026 to 0.2% on 26 October 2026.

References

Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.