---
title: "CVE-2021-4239\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-2021-4239?format=md
keywords: index, follow
---

# CVE-2021-4239

Publication date 27 December 2022

Last updated 11 July 2025

---

Ubuntu priority

**Medium**

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

## Cvss 3 Severity Score

**7.5 · High**

[Score breakdown](https://ubuntu.com/security/CVE-2021-4239?format=md#impact-score)

Toggle side navigation

## Description

The Noise protocol implementation suffers from weakened cryptographic
security after encrypting 2^64 messages, and a potential denial of service
attack. After 2^64 (~18.4 quintillion) messages are encrypted with the
Encrypt function, the nonce counter will wrap around, causing multiple
messages to be encrypted with the same key and nonce. In a separate issue,
the Decrypt function increments the nonce state even when it fails to
decrypt a message. If an attacker can provide an invalid input to the
Decrypt function, this will cause the nonce state to desynchronize between
the peers, resulting in a failure to encrypt all subsequent messages.

## Status

Show unmaintained releases

| Package | Ubuntu Release | Status |
| --- | --- | --- |
| golang-github-flynn-noise | 26.04 LTS resolute | Needs evaluation |
| 25.10 questing | Ignored end of life, was needs-triage |
| 25.04 plucky | Ignored end of life, was needs-triage |
| 24.10 oracular | Ignored end of life, was needs-triage |
| 24.04 LTS noble | Needs evaluation |
| 23.10 mantic | Ignored end of life, was needs-triage |
| 23.04 lunar | Ignored end of life, was needs-triage |
| 22.10 kinetic | Ignored end of life, was needs-triage |
| 22.04 LTS jammy | Needs evaluation |
| 20.04 LTS focal | Not in release |
| 18.04 LTS bionic | Not in release |
| 16.04 LTS xenial | Not in release |
| 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**

7.5 · High

* Base metrics

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

  | Parameter | Value |
  | --- | --- |
  | Base score | 7.5 · High |
  | Exploitability score | - |
  | Impact score | - |

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

## References

* [MITRE](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-4239)
* [NVD](https://nvd.nist.gov/vuln/detail/CVE-2021-4239)
* [Launchpad](https://launchpad.net/bugs/cve/CVE-2021-4239)
* [Debian](https://security-tracker.debian.org/tracker/CVE-2021-4239)

### Other references

* <https://github.com/flynn/noise/pull/44>
* <https://pkg.go.dev/vuln/GO-2022-0425>
* <https://www.cve.org/CVERecord?id=CVE-2021-4239>