# CVE-2021-34433: Auth bypass in Eclipse Californium

> Attackers can bypass DTLS server authentication by omitting the ServerKeyExchange signature, allowing man-in-the-middle attacks against Eclipse Californium users.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/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:** 20 Aug 2021
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-48jg-h3cv-mqvx

## What is CVE-2021-34433?

CVE-2021-34433 is a high-severity authentication bypass vulnerability in The Eclipse Foundation Eclipse Californium, published on 20 Aug 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

In Eclipse Californium version 2.0.0 to 2.6.4 and 3.0.0-M1 to 3.0.0-M3, the certificate based (x509 and RPK) DTLS handshakes accidentally succeeds without verifying the server side's signature on the client side, if that signature is not included in the server's ServerKeyExchange.

Weakness: CWE-347 (Improper Verification of Cryptographic Signature), CWE-322 (Key Exchange without Entity Authentication)

## Which versions are affected by CVE-2021-34433?

It affects 1 product.


Products: Eclipse Californium.

## How do I fix CVE-2021-34433?

No fix has been published for CVE-2021-34433 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-34433 being exploited?

There is no known exploitation of CVE-2021-34433 in the wild and no public exploit code.

## Other vulnerabilities in The Eclipse Foundation Eclipse Californium

- [CVE-2022-39368](https://insights.sbomify.com/CVE-2022-39368/): Californium Failing DTLS handshakes causes Data Loss due to throttling blocking processing of records (high 8.2)
- [CVE-2022-2576](https://insights.sbomify.com/CVE-2022-2576/): Eclipse Californium denial of service (DoS) via Datagram Transport Layer Security (DTLS) handshake on parameter mismatch (high 7.5)
- [CVE-2020-27222](https://insights.sbomify.com/CVE-2020-27222/): Denial of service in Eclipse Californium (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-34433 and fix it if it is affected.

What it is: CVE-2021-34433 is a high-severity authentication bypass vulnerability in The Eclipse Foundation Eclipse Californium, published on 20 Aug 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-2021-34433 in the wild and no public exploit code.

Affected product: The Eclipse Foundation Eclipse Californium. 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-2021-34433/ (Markdown: https://insights.sbomify.com/CVE-2021-34433/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-34433
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-34433
- OSV: https://osv.dev/vulnerability/CVE-2021-34433

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-34433/
Summaries are generated and may contain mistakes; the official description above is the record.