# CVE-2021-29455: Missing validation of JWT signature in `grassrootza/grassroot-platform`

> Attackers can forge valid JWTs due to missing signature verification during token refresh, enabling unauthorized access and potential privilege escalation.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 19 Apr 2021
- **Updated:** 3 Aug 2024

## What is CVE-2021-29455?

CVE-2021-29455 is a high-severity authentication bypass vulnerability in grassrootza grassroot-platform, published on 19 Apr 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Grassroot Platform is an application to make it faster, cheaper and easier to persistently organize and mobilize people in low-income communities. Grassroot Platform before master deployment as of 2021-04-16 did not properly verify the signature of JSON Web Tokens when refreshing an existing JWT. This allows to forge a valid JWT. The problem has been patched in version 1.3.1 by deprecating the JWT refresh function, which was an overdue deprecation regardless (the "refresh" flow is no longer used).

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

## Which versions are affected by CVE-2021-29455?

It affects 1 product.


Products: Grassroot Grassroot Platform.

## How do I fix CVE-2021-29455?

No fix has been published for CVE-2021-29455 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-29455 being exploited?

There is no known exploitation of CVE-2021-29455 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-29455 and fix it if it is affected.

What it is: CVE-2021-29455 is a high-severity authentication bypass vulnerability in grassrootza grassroot-platform, published on 19 Apr 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-29455 in the wild and no public exploit code.

Affected product: grassrootza grassroot-platform. 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-2021-29455/ (Markdown: https://insights.sbomify.com/CVE-2021-29455/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-29455
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-29455
- OSV: https://osv.dev/vulnerability/CVE-2021-29455

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-29455/
Summaries are generated and may contain mistakes; the official description above is the record.