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

> Attackers can bypass authentication and escalate privileges by tampering with JWS tokens due to missing signature validation in the reason-jose library.

- **Severity:** Medium 5.9 (`CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 1 Feb 2023
- **Updated:** 10 Mar 2025
- **Also known as:** GHSA-7jj9-6qwv-wpm7

## What is CVE-2023-23928?

CVE-2023-23928 is a medium-severity authentication bypass vulnerability in ulrikstrid reason-jose, published on 1 Feb 2023. Any signed-in user can exploit it over the network, with no action from the victim.

### Official 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.

Weakness: CWE-347 (Improper Verification of Cryptographic Signature)

## Which versions are affected by CVE-2023-23928?

It affects 1 product.


Products: Reason-Jose Project Reason-Jose.

## How do I fix CVE-2023-23928?

No fix has been published for CVE-2023-23928 yet. Limit exposure of the affected software until one is available.

## Is CVE-2023-23928 being exploited?

There is no known exploitation of CVE-2023-23928 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-23928 and fix it if it is affected.

What it is: CVE-2023-23928 is a medium-severity authentication bypass vulnerability in ulrikstrid reason-jose, published on 1 Feb 2023. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2023-23928 in the wild and no public exploit code.

Affected product: ulrikstrid reason-jose. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2023-23928/ (Markdown: https://insights.sbomify.com/CVE-2023-23928/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-23928
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-23928
- OSV: https://osv.dev/vulnerability/CVE-2023-23928

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-23928/
Summaries are generated and may contain mistakes; the official description above is the record.