--- title: "CVE-2020-15656\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-2020-15656?format=md keywords: index, follow --- # CVE-2020-15656 Publication date 29 July 2020 Last updated 25 August 2025 --- Ubuntu priority **Medium** [Why this priority?](https://ubuntu.com/security/cves/about#priority ) ## Cvss 3 Severity Score **8.8 · High** [Score breakdown](https://ubuntu.com/security/CVE-2020-15656?format=md#impact-score) Toggle side navigation ## Description JIT optimizations involving the Javascript arguments object could confuse later optimizations. This risk was already mitigated by various precautions in the code, resulting in this bug rated at only moderate severity. This vulnerability affects Firefox ESR < 78.1, Firefox < 79, and Thunderbird < 78.1. [Read the notes from the security team](https://ubuntu.com/security/CVE-2020-15656?format=md#notes) ## Status Show unmaintained releases | Package | Ubuntu Release | Status | | --- | --- | --- | | firefox | 24.04 LTS noble | Fixed 80.0.1+build1-0ubuntu1 | | 23.10 mantic | Fixed 80.0.1+build1-0ubuntu1 | | 23.04 lunar | Fixed 80.0.1+build1-0ubuntu1 | | 22.10 kinetic | Fixed 80.0.1+build1-0ubuntu1 | | 22.04 LTS jammy | Fixed 80.0.1+build1-0ubuntu1 | | 21.10 impish | Fixed 80.0.1+build1-0ubuntu1 | | 21.04 hirsute | Fixed 80.0.1+build1-0ubuntu1 | | 20.10 groovy | Fixed 80.0.1+build1-0ubuntu1 | | 20.04 LTS focal | Fixed 79.0+build1-0ubuntu0.20.04.1 | | 18.04 LTS bionic | Fixed 79.0+build1-0ubuntu0.18.04.1 | | 16.04 LTS xenial | Fixed 79.0+build1-0ubuntu0.16.04.2 | | 14.04 LTS trusty | Not in release | | mozjs38 | 24.04 LTS noble | Not in release | | 23.10 mantic | Not in release | | 23.04 lunar | Not in release | | 22.10 kinetic | Not in release | | 22.04 LTS jammy | Not in release | | 21.10 impish | Not in release | | 21.04 hirsute | Not in release | | 20.10 groovy | Not in release | | 20.04 LTS focal | Not in release | | 18.04 LTS bionic | Ignored | | 16.04 LTS xenial | Not in release | | 14.04 LTS trusty | Not in release | | mozjs52 | 24.04 LTS noble | Not in release | | 23.10 mantic | Not in release | | 23.04 lunar | Not in release | | 22.10 kinetic | Not in release | | 22.04 LTS jammy | Not in release | | 21.10 impish | Not in release | | 21.04 hirsute | Not in release | | 20.10 groovy | Ignored end of life | | 20.04 LTS focal | Ignored | | 18.04 LTS bionic | Ignored | | 16.04 LTS xenial | Not in release | | 14.04 LTS trusty | Not in release | | mozjs60 | 24.04 LTS noble | Not in release | | 23.10 mantic | Not in release | | 23.04 lunar | Not in release | | 22.10 kinetic | Not in release | | 22.04 LTS jammy | Not in release | | 21.10 impish | Not in release | | 21.04 hirsute | Not in release | | 20.10 groovy | Not in release | | 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 | | mozjs68 | 24.04 LTS noble | Not in release | | 23.10 mantic | Not in release | | 23.04 lunar | Not in release | | 22.10 kinetic | Not in release | | 22.04 LTS jammy | Not in release | | 21.10 impish | Not in release | | 21.04 hirsute | Not in release | | 20.10 groovy | Ignored end of life | | 20.04 LTS focal | Ignored | | 18.04 LTS bionic | Not in release | | 16.04 LTS xenial | Not in release | | 14.04 LTS trusty | Not in release | | thunderbird | 24.04 LTS noble | Not affected | | 23.10 mantic | Not affected | | 23.04 lunar | Not affected | | 22.10 kinetic | Not affected | | 22.04 LTS jammy | Not affected | | 21.10 impish | Not affected | | 21.04 hirsute | Not affected | | 20.10 groovy | Not affected | | 20.04 LTS focal | Fixed 1:78.7.1+build1-0ubuntu0.20.04.1 | | 18.04 LTS bionic | Fixed 1:78.8.1+build1-0ubuntu0.18.04.1 | | 16.04 LTS xenial | Ignored end of standard support, was needs-triage | | 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) ## Notes --- ### [tyhicks](https://launchpad.net/~tyhicks) mozjs contains a copy of the SpiderMonkey JavaScript engine ## Severity score breakdown CVSS version: CVSS v3.0 **Base score** 8.8 · High * Base metrics | Parameter | Value | | --- | --- | | Attack vector | Network | | Attack complexity | Low | | Privileges required | None | | User interaction | Required | | Scope | Unchanged | | Confidentiality impact | High | | Integrity impact | High | | Availability impact | High | * Scores | Parameter | Value | | --- | --- | | Base score | 8.8 · High | | Exploitability score | - | | Impact score | - | **Vector:** CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H ## References * [MITRE](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-15656) * [NVD](https://nvd.nist.gov/vuln/detail/CVE-2020-15656) * [Launchpad](https://launchpad.net/bugs/cve/CVE-2020-15656) * [Debian](https://security-tracker.debian.org/tracker/CVE-2020-15656) ### Related Ubuntu Security Notices (USN) + [USN-4443-1](https://usn.ubuntu.com/USN-4443-1) + Firefox vulnerabilities + 29 July 2020 ### Other references * * *