# GHSA-8v5f-hp78-jgxq: Signature Verification Bypass in jwt-simple

> An attacker can bypass JWT signature verification by exploiting algorithm confusion, allowing unauthorized access to protected resources.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 6 Jun 2019

## What is GHSA-8v5f-hp78-jgxq?

GHSA-8v5f-hp78-jgxq is a vulnerability in jwt-simple, published on 6 Jun 2019. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Versions of `jwt-simple` prior to 0.5.3 are vulnerable to Signature Verification Bypass. If no algorithm is specified in the `decode()` function, the packages uses the algorithm in the JWT to decode tokens. This allows an attacker to create a HS256 (symmetric algorithm) JWT with the server's public key as secret, and the package will verify it as HS256 instead of RS256 (asymmetric algorithm).

## Recommendation

Upgrade to version 0.5.3 or later.

## Which versions are affected by GHSA-8v5f-hp78-jgxq?

2 open source packages ship an affected version, including jwt-simple.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `jwt-simple` | npm | All versions | 0.5.3 |
| `jwt-simple` | npm | All versions | 0.5.3 |

## How do I fix GHSA-8v5f-hp78-jgxq?

Upgrade jwt-simple to 0.5.3 or later.

## Is GHSA-8v5f-hp78-jgxq being exploited?

There is no known exploitation of GHSA-8v5f-hp78-jgxq in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for GHSA-8v5f-hp78-jgxq and fix it if it is affected.

What it is: GHSA-8v5f-hp78-jgxq is a vulnerability in jwt-simple, published on 6 Jun 2019. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of GHSA-8v5f-hp78-jgxq in the wild and no public exploit code.

Affected packages and fixed versions:
- jwt-simple (npm): affected all versions; fixed in 0.5.3
- jwt-simple (npm): affected all versions; fixed in 0.5.3

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/GHSA-8v5f-hp78-jgxq/ (Markdown: https://insights.sbomify.com/GHSA-8v5f-hp78-jgxq/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/GHSA-8v5f-hp78-jgxq

---
From sbomify Insights: https://insights.sbomify.com/GHSA-8v5f-hp78-jgxq/
Summaries are generated and may contain mistakes; the official description above is the record.