---
title: "CVE-2026-42011\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-2026-42011?format=md
keywords: index, follow
---

# CVE-2026-42011

Publication date 7 May 2026

Last updated 16 July 2026

---

Ubuntu priority

**Medium**

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

## Cvss 3 Severity Score

**7.4 · High**

[Score breakdown](https://ubuntu.com/security/CVE-2026-42011?format=md#impact-score)

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## Description

A flaw was found in gnutls. This vulnerability occurs because permitted
name constraints were incorrectly ignored when previous Certificate
Authorities (CAs) only had excluded name constraints. A remote attacker
could exploit this to bypass critical name constraint checks during
certificate validation. This bypass could lead to the acceptance of invalid
certificates, potentially enabling spoofing or man-in-the-middle attacks
against affected systems.

[Read the notes from the security team](https://ubuntu.com/security/CVE-2026-42011?format=md#notes)

## Status

Show unmaintained releases

| Package | Ubuntu Release | Status |
| --- | --- | --- |
| gnutls28 | 26.04 LTS resolute | Fixed 3.8.12-2ubuntu1.1 |
| 25.10 questing | Fixed 3.8.9-3ubuntu2.2 |
| 24.04 LTS noble | Fixed 3.8.3-1.1ubuntu3.6 |
| 22.04 LTS jammy | Fixed 3.7.3-4ubuntu1.9 |
| 20.04 LTS focal | Fixed 3.6.13-2ubuntu1.12+esm3  Ubuntu Pro |
| 18.04 LTS bionic | Fixed 3.5.18-1ubuntu1.6+esm4  Ubuntu Pro |
| 16.04 LTS xenial | Not affected |

---

* [How can I get the fixes?](https://ubuntu.com/security/cves/about#security)
* [What do statuses mean?](https://ubuntu.com/security/cves/about#statuses)
* [Patch details](https://ubuntu.com/security/CVE-2026-42011?format=md#patch-details)

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## Notes

---

### [mrmajumder](https://launchpad.net/~mrmajumder)

xenial is not-affected, the vulnerable empty-permitted
intersection short-circuit was introduced after 3.4.10.

### Patch details

For informational purposes only. We recommend not to cherry-pick updates. [How can I get the fixes?](https://ubuntu.com/security/cves/about#security)

| Package | Patch details |
| --- | --- |
| gnutls28 | * Upstream:   [1dead2f](https://gitlab.com/gnutls/gnutls/-/commit/1dead2faec6320aaba321eb56f20d442df192b83) |

## Severity score breakdown

CVSS version:
CVSS v3.0

**Base score**

7.4 · High

* Base metrics

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

  | Parameter | Value |
  | --- | --- |
  | Base score | 7.4 · High |
  | Exploitability score | - |
  | Impact score | - |

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

## References

* [MITRE](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2026-42011)
* [NVD](https://nvd.nist.gov/vuln/detail/CVE-2026-42011)
* [Launchpad](https://launchpad.net/bugs/cve/CVE-2026-42011)
* [Debian](https://security-tracker.debian.org/tracker/CVE-2026-42011)

### Related Ubuntu Security Notices (USN)

+ [USN-8284-1](https://usn.ubuntu.com/USN-8284-1)
+ GnuTLS vulnerabilities
+ 20 May 2026

+ [USN-8539-1](https://usn.ubuntu.com/USN-8539-1)
+ GnuTLS vulnerabilities
+ 14 July 2026

### Other references

* <https://www.cve.org/CVERecord?id=CVE-2026-42011>
* <https://www.gnutls.org/security-new.html#GNUTLS-SA-2026-04-29-6>