---
title: "CVE-2026-34872\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-2026-34872?format=md
keywords: index, follow
---

# CVE-2026-34872

Publication date 1 April 2026

Last updated 8 April 2026

---

Ubuntu priority

**Medium**

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

## Cvss 3 Severity Score

**9.1 · Critical**

[Score breakdown](https://ubuntu.com/security/CVE-2026-34872?format=md#impact-score)

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## Description

An issue was discovered in Mbed TLS 3.5.x and 3.6.x through 3.6.5 and
TF-PSA-Crypto 1.0. There is a lack of contributory behavior in FFDH due to
improper input validation. Using finite-field Diffie-Hellman, the other
party can force the shared secret into a small set of values (lack of
contributory behavior). This is a problem for protocols that depend on
contributory behavior (which is not the case for TLS). The attack can be
carried by the peer, or depending on the protocol by an active network
attacker (person in the middle).

## Status

Show unmaintained releases

| Package | Ubuntu Release | Status |
| --- | --- | --- |
| mbedtls | 26.04 LTS resolute | Needs evaluation |
| 25.10 questing | Ignored end of life, was needs-triage |
| 24.04 LTS noble | Needs evaluation |
| 22.04 LTS jammy | Needs evaluation |
| 20.04 LTS focal | Needs evaluation |
| 18.04 LTS bionic | Needs evaluation |
| 16.04 LTS xenial | Needs evaluation |

---

* [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**

9.1 · Critical

* Base metrics

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

  | Parameter | Value |
  | --- | --- |
  | Base score | 9.1 · Critical |
  | Exploitability score | - |
  | Impact score | - |

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

## References

* [MITRE](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2026-34872)
* [NVD](https://nvd.nist.gov/vuln/detail/CVE-2026-34872)
* [Launchpad](https://launchpad.net/bugs/cve/CVE-2026-34872)
* [Debian](https://security-tracker.debian.org/tracker/CVE-2026-34872)

### Other references

* <https://www.cve.org/CVERecord?id=CVE-2026-34872>
* <https://mbed-tls.readthedocs.io/en/latest/security-advisories/mbedtls-security-advisory-2026-03-ffdh-peerkey-checks/>
* <https://mbed-tls.readthedocs.io/en/latest/security-advisories/>