# ruby-jwt: Empty-key HMAC bypass; cross-language sibling of CVE-2026-44351

Advisory record · `GHSA-c32j-vqhx-rx3x`

- **Identifiers:** `GHSA-c32j-vqhx-rx3x` · `CVE-2026-45363`
- **State:** Confirmed
- **Severity:** CVSS 9.1 Critical
- **Critical:** Yes: CVSS 9+
- **Weakness (CWE):** [CWE-287](https://cwe.mitre.org/data/definitions/287.html) · [CWE-326](https://cwe.mitre.org/data/definitions/326.html) · [CWE-1391](https://cwe.mitre.org/data/definitions/1391.html)
- **Tags:** [Authentication bypass](https://agentprime.io/advisories/tag/auth-bypass.md) · [Weak cryptography or TLS](https://agentprime.io/advisories/tag/weak-crypto.md) · [Hard-coded credentials](https://agentprime.io/advisories/tag/hard-coded-credentials.md)
- **Published:** 18 May 2026
- **Updated:** 10 Sept 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 18 May 2026, 17:24 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Critical

Critical, because:

- CVSS score 9.1: 9.0 or more.

How we decide what’s critical: <https://agentprime.io/advisories/critical.md>

## Affected packages

- `jwt` (RubyGems): affected `>=3.0.0, <3.2.0 || <2.10.3`; fixed in `3.2.0`, `2.10.3`

## Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

## Severity and exploitation

- 9.1 Critical, CVSS 3.1: `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N`, from CNA (GitHub_M)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0036, the 30th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 31 Oct 2026, 15:16 UTC: First seen by agentprime
- 31 Oct 2026, 15:16 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-c32j-vqhx-rx3x)

## Sources

- [GitHub Advisory Database: GHSA-c32j-vqhx-rx3x](https://github.com/advisories/GHSA-c32j-vqhx-rx3x)
- [OSV: GHSA-c32j-vqhx-rx3x](https://osv.dev/vulnerability/GHSA-c32j-vqhx-rx3x)
- <https://github.com/jwt/ruby-jwt/security/advisories/GHSA-c32j-vqhx-rx3x>
- <https://github.com/jwt/ruby-jwt/issues/724>
- <https://github.com/jwt/ruby-jwt/commit/db560b769a07bd9724e77ff505011ac01872106f>
- <https://github.com/jwt/ruby-jwt>
- <https://github.com/jwt/ruby-jwt/releases/tag/v2.10.3>
- <https://github.com/jwt/ruby-jwt/releases/tag/v3.2.0>
- <https://github.com/rubysec/ruby-advisory-db/blob/master/gems/jwt/CVE-2026-45363.yml>
- <https://www.cve.org/CVERecord?id=CVE-2026-45363>

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-c32j-vqhx-rx3x>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

---

The web page: <https://agentprime.io/advisories/GHSA-c32j-vqhx-rx3x/>. Everything for agents: <https://agentprime.io/llms.txt>.