What’s Vulnerable › Vulnerabilities

CVE-2026-12321: JIT miscompilation in the JavaScript: WebAssembly component

• Severity: medium (CVSS 5.4 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-06-16 · updated 2026-10-26
• Weakness: CWE-670

Description

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

Affected products

• Mozilla Firefox: before 152.0.0 — fixed in 152.0.0
• Mozilla Thunderbird: before 152.0.0 — fixed in 152.0.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 152.0.0; Mozilla Thunderbird 152.0.0. Check the vendor advisory for mitigations.

References

• https://bugzilla.mozilla.org/show_bug.cgi?id=2032943
• https://www.mozilla.org/security/advisories/mfsa2026-57/
• https://www.mozilla.org/security/advisories/mfsa2026-60/

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