# CVE-2023-6937: Improper (D)TLS key boundary enforcement


- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 15 Feb 2024
- **Updated:** 24 Apr 2025
- **Also known as:** DEBIAN-CVE-2023-6937, GHSA-ff3x-q8pg-rh37, JLSEC-2026-679, UBUNTU-CVE-2023-6937

## What is CVE-2023-6937?

CVE-2023-6937 is a medium-severity vulnerability in Wolfssl Wolfssl, published on 15 Feb 2024. 

### Official description

wolfSSL prior to 5.6.6 did not check that messages in one (D)TLS record do not span key boundaries. As a result, it was possible to combine (D)TLS messages using different keys into one (D)TLS record. The most extreme edge case is that, in (D)TLS 1.3, it was possible that an unencrypted (D)TLS 1.3 record from the server containing first a ServerHello message and then the rest of the first server flight would be accepted by a wolfSSL client. In (D)TLS 1.3 the handshake is encrypted after the ServerHello but a wolfSSL client would accept an unencrypted flight from the server. This does not compromise key negotiation and authentication so it is assigned a low severity rating.

Weakness: CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2023-6937?

It affects 1 product.


Products: Wolfssl Wolfssl.

## How do I fix CVE-2023-6937?

Upgrade to a fixed version.

## Is CVE-2023-6937 being exploited?

There is no known exploitation of CVE-2023-6937 in the wild and no public exploit code.

## Other vulnerabilities in Wolfssl Wolfssl

- [CVE-2024-5991](https://insights.sbomify.com/CVE-2024-5991/): Buffer overread in domain name matching (critical 10.0)
- [CVE-2021-37155](https://insights.sbomify.com/CVE-2021-37155/): Security feature bypass in n/a (critical 9.8)
- [CVE-2020-36177](https://insights.sbomify.com/CVE-2020-36177/): Memory corruption in n/a (critical 9.8)
- [CVE-2014-2896](https://insights.sbomify.com/CVE-2014-2896/): Memory corruption in n/a (critical 9.8)
- [CVE-2014-2897](https://insights.sbomify.com/CVE-2014-2897/): Memory corruption in n/a (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-6937 and fix it if it is affected.

What it is: CVE-2023-6937 is a medium-severity vulnerability in Wolfssl Wolfssl, published on 15 Feb 2024. 
Exploitation: There is no known exploitation of CVE-2023-6937 in the wild and no public exploit code.

Affected product: Wolfssl Wolfssl. 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-2023-6937/ (Markdown: https://insights.sbomify.com/CVE-2023-6937/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-6937
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-6937
- OSV: https://osv.dev/vulnerability/CVE-2023-6937

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-6937/
Summaries are generated and may contain mistakes; the official description above is the record.