---
title: "CVE-2026-6786\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-2026-6786?format=md
keywords: index, follow
---

# CVE-2026-6786

Publication date 26 April 2026

Last updated 27 May 2026

---

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-2026-6786?format=md#impact-score)

Toggle side navigation

## Description

Memory safety bugs present in Firefox ESR 140.9, Thunderbird ESR 140.9,
Firefox 149 and Thunderbird 149. Some of these bugs showed evidence of
memory corruption and we presume that with enough effort some of these
could have been exploited to run arbitrary code. This vulnerability was
fixed in Firefox 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird
140.10.

[Read the notes from the security team](https://ubuntu.com/security/CVE-2026-6786?format=md#notes)

## Status

Show unmaintained releases

| Package | Ubuntu Release | Status |
| --- | --- | --- |
| firefox | 26.04 LTS resolute | Not affected |
| 25.10 questing | Not affected |
| 24.04 LTS noble | Not affected |
| 22.04 LTS jammy | Not affected |
| mozjs102 | 26.04 LTS resolute | Not in release |
| 25.10 questing | Not in release |
| 24.04 LTS noble | Ignored |
| 22.04 LTS jammy | Ignored |
| mozjs115 | 26.04 LTS resolute | Not in release |
| 25.10 questing | Not in release |
| 24.04 LTS noble | Ignored |
| 22.04 LTS jammy | Not in release |
| mozjs38 | 26.04 LTS resolute | Not in release |
| 25.10 questing | Not in release |
| 24.04 LTS noble | Not in release |
| 22.04 LTS jammy | Not in release |
| 18.04 LTS bionic | Needs evaluation |
| mozjs52 | 26.04 LTS resolute | Not in release |
| 25.10 questing | Not in release |
| 24.04 LTS noble | Not in release |
| 22.04 LTS jammy | Not in release |
| 20.04 LTS focal | Ignored |
| 18.04 LTS bionic | Ignored |
| mozjs68 | 26.04 LTS resolute | Not in release |
| 25.10 questing | Not in release |
| 24.04 LTS noble | Not in release |
| 22.04 LTS jammy | Not in release |
| 20.04 LTS focal | Ignored |
| mozjs78 | 26.04 LTS resolute | Not in release |
| 25.10 questing | Not in release |
| 24.04 LTS noble | Not in release |
| 22.04 LTS jammy | Ignored |
| mozjs91 | 26.04 LTS resolute | Not in release |
| 25.10 questing | Not in release |
| 24.04 LTS noble | Not in release |
| 22.04 LTS jammy | Ignored |
| thunderbird | 26.04 LTS resolute | Not affected |
| 25.10 questing | Not affected |
| 24.04 LTS noble | Not affected |
| 22.04 LTS jammy | Vulnerable |

---

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

## Notes

---

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

mozjs\* contain a copy of the SpiderMonkey JavaScript engine. It
is not feasible to backport security fixes to the mozjs\*
packages, as such, marking them as ignored.
starting with Ubuntu 22.04, the firefox package is just a script
that installs the Firefox snap
starting with Ubuntu 24.04, the thunderbird package is just a
script that installs the Thunderbird snap

## Severity score breakdown

CVSS version:
CVSS v3.0

**Base score**

7.5 · High

* Base metrics

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

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

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

## References

* [MITRE](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2026-6786)
* [NVD](https://nvd.nist.gov/vuln/detail/CVE-2026-6786)
* [Launchpad](https://launchpad.net/bugs/cve/CVE-2026-6786)
* [Debian](https://security-tracker.debian.org/tracker/CVE-2026-6786)

### Other references

* <https://www.cve.org/CVERecord?id=CVE-2026-6786>
* <https://www.mozilla.org/en-US/security/advisories/mfsa2026-30/#CVE-2026-6786>
* <https://www.mozilla.org/en-US/security/advisories/mfsa2026-32/#CVE-2026-6786>