---
id: "CVE-2026-54238"
kind: "vulnerability"
aliases: ["CVE-2026-54238"]
title: "Supabase Realtime: expired JWT accepted when exp is a string"
severity: "low"
cvss: 3.1
epss: 0.00206
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["realtime", "runtime", "self-hosted", "supabase", "websockets"]
not_affected_if: ["patched-version"]
published_at: "2026-10-22T18:17:28+00:00"
first_seen_at: "2026-10-23T21:57:31+00:00"
updated_at: "2026-10-25T04:47:20+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-54238", "first_seen_at": "2026-10-23T21:57:31+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-54238", "first_seen_at": "2026-10-24T07:15:51+00:00"}]
---

# Supabase Realtime: expired JWT accepted when exp is a string

Supabase Realtime's REST broadcast endpoints accept an expired JWT when its exp claim is encoded as a JSON string rather than a number. An attacker holding such a token can push broadcast messages to subscribers of a project.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the Supabase Realtime server version and compare it with `2.103.1`
- Review whether the project uses the REST broadcast endpoints (unknown if the sources say more)

## Fix

- Upgrade Supabase Realtime to `2.103.1` or later

## Timeline

- 2026-10-23T21:57:31+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-54238
- 2026-10-24T07:15:51+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2026-54238

## From the sources

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.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_