# CVE-2024-42350: Public key confusion in third party block in Biscuit

> A malicious user can trick a third-party authority into generating tokens trusting the wrong keypair, bypassing authorization checks in Biscuit implementations.

- **Severity:** Low 3.0 (`CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:N/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 5 Aug 2024
- **Updated:** 5 Aug 2024

## What is CVE-2024-42350?

CVE-2024-42350 is a low-severity authentication bypass vulnerability in biscuit-auth biscuit, published on 5 Aug 2024. An attacker needs administrator access to exploit it, with no action from the victim.

### Official description

Biscuit is an authorization token with decentralized verification, offline attenuation and strong security policy enforcement based on a logic language. Third-party blocks can be generated without transferring the whole token to the third-party authority. Instead, a `ThirdPartyBlock` request can be sent, providing only the necessary info to generate a third-party block and to sign it: 1. the public key of the previous block (used in the signature), 2. the public keys part of the token symbol table (for public key interning in datalog expressions). A third-part block request forged by a malicious user can trick the third-party authority into generating datalog trusting the wrong keypair. Tokens with third-party blocks containing `trusted` annotations generated through a third party block request. This has been addressed in version 4 of the specification. Users are advised to update their implementations to conform. There are no known workarounds for this vulnerability.

Weakness: CWE-668 (Exposure of Resource to Wrong Sphere)

## Which versions are affected by CVE-2024-42350?


## How do I fix CVE-2024-42350?

Upgrade to a fixed version.

## Is CVE-2024-42350 being exploited?

There is no known exploitation of CVE-2024-42350 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2024-42350 and fix it if it is affected.

What it is: CVE-2024-42350 is a low-severity authentication bypass vulnerability in biscuit-auth biscuit, published on 5 Aug 2024. An attacker needs administrator access to exploit it, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2024-42350 in the wild and no public exploit code.

Affected product: biscuit-auth biscuit. 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-2024-42350/ (Markdown: https://insights.sbomify.com/CVE-2024-42350/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-42350
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-42350
- OSV: https://osv.dev/vulnerability/CVE-2024-42350

---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-42350/
Summaries are generated and may contain mistakes; the official description above is the record.