CVE-2026-12321

JIT miscompilation in the JavaScript: WebAssembly component

5.4 Medium

JIT miscompilation in the JavaScript: WebAssembly component. This vulnerability was fixed in Firefox 152 and Thunderbird 152.

Attack profile

How easy it is to exploit

Attack vector: Network
Complexity: Low
Privileges needed: None
User interaction: Required

What an attacker can affect

Confidentiality: Low
Integrity: Low
Availability: None

Exploit likelihood

0.16%Unchanged since Jun 17, 2026

What each source reports

CVE List Score used 5.4

JIT miscompilation in the JavaScript: WebAssembly component

JIT miscompilation in the JavaScript: WebAssembly component. This vulnerability was fixed in Firefox 152 and Thunderbird 152.

Record: CVE-2026-12321
CVSS 3.1: 5.4 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N
Weakness: CWE-670
Updated: 2026-11-02

EUVDEUVD-2026-37067 5.4

JIT miscompilation in the JavaScript: WebAssembly component. This vulnerability was fixed in Firefox 152 and Thunderbird 152.

Record: EUVD-2026-37067
CVSS 3.1: 5.4 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N
Updated: 2026-11-02

GitHub AdvisoriesGHSA-r946-vv6g-44hh 5.4

JIT miscompilation in the JavaScript: WebAssembly component. This vulnerability was fixed in...

JIT miscompilation in the JavaScript: WebAssembly component. This vulnerability was fixed in Firefox 152.

Record: GHSA-r946-vv6g-44hh
CVSS 3.1: 5.4 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N
Weakness: CWE-670
Updated: 2026-11-02

NVD 5.4

JIT miscompilation in the JavaScript: WebAssembly component. This vulnerability was fixed in Firefox 152 and Thunderbird 152.

Record: CVE-2026-12321
CVSS 3.1: 5.4 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N
Weakness: CWE-670
Updated: 2026-11-02

OSVUBUNTU-CVE-2026-12321 5.4

JIT miscompilation in the JavaScript: WebAssembly component. This vulnerability was fixed in Firefox 152 and Thunderbird 152.

Record: UBUNTU-CVE-2026-12321
CVSS 3.1: 5.4 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N
Updated: 2026-11-02

OSVopenSUSE-SU-2026:11052-1 No score

MozillaFirefox-152.0-1.1 on GA media

These are all security issues fixed in the MozillaFirefox-152.0-1.1 package on the GA media of openSUSE Tumbleweed.

Record: openSUSE-SU-2026:11052-1
Updated: 2026-11-02

OSVopenSUSE-SU-2026:11373-1 No score

firefox-esr-153.0-1.1 on GA media

These are all security issues fixed in the firefox-esr-153.0-1.1 package on the GA media of openSUSE Tumbleweed.

Record: openSUSE-SU-2026:11373-1
Updated: 2026-11-02

Affected products

Affected packages

Affected packages
Package	Affected	Fixed
`mozjs52` Ubuntu:18.04:LTS	All versions, plus listed versions 52.3.1-0ubuntu352.3.1-7fakesync152.8.1-0ubuntu0.18.04.152.9.1-0ubuntu0.18.04.1	None known
`mozjs38` Ubuntu:18.04:LTS	All versions, plus listed versions 38.8.0~repack1-0ubuntu138.8.0~repack1-0ubuntu338.8.0~repack1-0ubuntu4	None known
`mozjs68` Ubuntu:20.04:LTS	All versions, plus listed versions 68.5.0-1~fakesync68.5.0-2~fakesync68.6.0-168.6.0-1ubuntu1	None known
`mozjs52` Ubuntu:20.04:LTS	All versions, plus listed versions 52.9.1-1build152.9.1-1ubuntu3	None known
`mozjs102` Ubuntu:22.04:LTS	All versions, plus listed versions 102.11.0-0ubuntu0.22.04.1102.12.0-0ubuntu0.22.04.1102.13.0-0ubuntu0.22.04.1102.15.1-0ubuntu0.22.04.1	None known
`mozjs78` Ubuntu:22.04:LTS	All versions, plus listed versions 78.13.0-178.15.0-278.15.0-4ubuntu1	None known
`mozjs91` Ubuntu:22.04:LTS	All versions, plus listed versions 91.5.1-0ubuntu191.6.0-191.6.0-291.7.0-291.10.0-0ubuntu1	None known
`thunderbird` Ubuntu:22.04:LTS	All versions, plus listed versions 1:91.1.2+build1-0ubuntu11:91.3.0+build2-0ubuntu11:91.3.1+build1-0ubuntu11:91.3.2+build1-0ubuntu11:91.4.0+build1.1-0ubuntu1 Show 34 moreShow less 1:91.4.0+build2-0ubuntu11:91.5.0+build1-0ubuntu11:91.5.1+build1-0ubuntu11:91.6.1+build1-0ubuntu11:91.7.0+build1-0ubuntu11:91.7.0+build2-0ubuntu11:91.8.0+build2-0ubuntu11:91.9.1+build1-0ubuntu0.22.04.11:91.11.0+build2-0ubuntu0.22.04.11:102.2.2+build1-0ubuntu0.22.04.11:102.4.2+build2-0ubuntu0.22.04.11:102.7.1+build2-0ubuntu0.22.04.11:102.8.0+build2-0ubuntu0.22.04.11:102.9.0+build1-0ubuntu0.22.04.11:102.10.0+build2-0ubuntu0.22.04.11:102.11.0+build1-0ubuntu0.22.04.11:102.13.0+build1-0ubuntu0.22.04.11:102.15.0+build1-0ubuntu0.22.04.11:102.15.1+build1-0ubuntu0.22.04.11:115.3.1+build1-0ubuntu0.22.04.21:115.4.1+build1-0ubuntu0.22.04.11:115.5.0+build1-0ubuntu0.22.04.11:115.6.0+build2-0ubuntu0.22.04.11:115.8.1+build1-0ubuntu0.22.04.11:115.9.0+build1-0ubuntu0.22.04.11:115.10.1+build1-0ubuntu0.22.04.11:115.11.0+build2-0ubuntu0.22.04.11:115.12.0+build3-0ubuntu0.22.04.11:115.13.0+build5-0ubuntu0.22.04.11:115.15.0+build1-0ubuntu0.22.04.11:115.16.0+build2-0ubuntu0.22.04.11:115.18.0+build1-0ubuntu0.22.04.11:128.12.0+build1-0ubuntu0.22.04.11:140.7.1+build1-0ubuntu0.22.04.1	None known
`mozjs102` Ubuntu:24.04:LTS	All versions, plus listed versions 102.15.1-1102.15.1-3ubuntu2	None known
`mozjs115` Ubuntu:24.04:LTS	All versions, plus listed versions 115.3.0-0ubuntu1115.4.0-2115.5.0-1115.6.0-1115.7.0-4 Show 4 moreShow less 115.8.0-1115.9.0-1115.9.0-1build1115.10.0-1	None known
`MozillaFirefox` openSUSE:Tumbleweed From an advisory covering 40 CVEs	before 152.0-1.1	152.0-1.1
`firefox-esr` openSUSE:Tumbleweed From an advisory covering 228 CVEs	before 153.0-1.1	153.0-1.1

History

History
Recorded	Changed	Sources
Nov 6, 2026	affected, facts
Nov 2, 2026	first indexed	CVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-12321 is a medium vulnerability (CVSS 5.4) in Mozilla Firefox, published June 16, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.16%, the 5th percentile. No source names a fixed version.

References

Show 194 moreShow less

This page doesn't list everything

Left out here: 63 references. The JSON record has them.