---
title: "CVE-2023-6937\n    | Ubuntu"
description: Ubuntu is an open source software operating system that runs from the
  desktop, to the cloud, to all your internet connected things.
url: https://ubuntu.com/security/CVE-2023-6937?format=md
keywords: index, follow
---

# CVE-2023-6937

Publication date 15 February 2024

Last updated 26 August 2025

---

Ubuntu priority

**Medium**

[Why this priority?](https://ubuntu.com/security/cves/about#priority )

## Cvss 3 Severity Score

**5.3 · Medium**

[Score breakdown](https://ubuntu.com/security/CVE-2023-6937?format=md#impact-score)

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## 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.

## Status

Show unmaintained releases

| Package | Ubuntu Release | Status |
| --- | --- | --- |
| wolfssl | 26.04 LTS resolute | Not affected |
| 25.10 questing | Not affected |
| 25.04 plucky | Not affected |
| 24.10 oracular | Not affected |
| 24.04 LTS noble | Not affected |
| 23.10 mantic | Ignored end of life, was needs-triage |
| 23.04 lunar | Ignored end of life, was needs-triage |
| 22.04 LTS jammy | Needs evaluation |
| 20.04 LTS focal | Needs evaluation |
| 18.04 LTS bionic | Needs evaluation |
| 16.04 LTS xenial | Needs evaluation |
| 14.04 LTS trusty | Not in release |

---

* [How can I get the fixes?](https://ubuntu.com/security/cves/about#security)
* [What do statuses mean?](https://ubuntu.com/security/cves/about#statuses)

## Severity score breakdown

CVSS version:
CVSS v3.0

**Base score**

5.3 · Medium

* Base metrics

  | Parameter | Value |
  | --- | --- |
  | Attack vector | Network |
  | Attack complexity | Low |
  | Privileges required | None |
  | User interaction | None |
  | Scope | Unchanged |
  | Confidentiality impact | Low |
  | Integrity impact | None |
  | Availability impact | None |
* Scores

  | Parameter | Value |
  | --- | --- |
  | Base score | 5.3 · Medium |
  | Exploitability score | - |
  | Impact score | - |

**Vector:** CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

## References

* [MITRE](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-6937)
* [NVD](https://nvd.nist.gov/vuln/detail/CVE-2023-6937)
* [Launchpad](https://launchpad.net/bugs/cve/CVE-2023-6937)
* [Debian](https://security-tracker.debian.org/tracker/CVE-2023-6937)

### Other references

* <https://github.com/wolfSSL/wolfssl/blob/v5.6.6-stable/ChangeLog.md#vulnerabilities>
* <https://www.cve.org/CVERecord?id=CVE-2023-6937>