CVE-2026-16363

CRITICAL

Published Jul 21, 2026 Modified Jul 24, 2026 CWE-682 CWE-843

Description

JIT miscompilation in the JavaScript: WebAssembly component. This vulnerability was fixed in Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13.

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CVSS v3.1 Score

9.8

CRITICAL

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

EPSS — Exploit Prediction

0.0044

Probability of exploitation

0.36%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-682 CWE-682

CWE-843 CWE-843

Affected Products

Vendor	Product	Versions
mozilla	firefox	< 140.13.0
mozilla	firefox	< 153.0.0
mozilla	thunderbird	< 140.13.0
mozilla	thunderbird	141.0 — 153.0

References

Advisories & Patches

https://www.mozilla.org/security/advisories/mfsa2026-68/ https://www.mozilla.org/security/advisories/mfsa2026-70/ https://www.mozilla.org/security/advisories/mfsa2026-71/ https://www.mozilla.org/security/advisories/mfsa2026-72/

Other References

https://bugzilla.mozilla.org/show_bug.cgi?id=2047689

Frequently Asked Questions

What is CVE-2026-16363? +

JIT miscompilation in the JavaScript: WebAssembly component. This vulnerability was fixed in Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13. It has a CVSS v3.1 base score of 9.8 (CRITICAL).

How severe is CVE-2026-16363? +

CVE-2026-16363 has a CVSS v3.1 score of 9.8 out of 10, rated CRITICAL. This is a critical vulnerability that should be patched immediately. The EPSS score is 0.0044, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-16363? +

CVE-2026-16363 affects products from mozilla, specifically: firefox, thunderbird. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-16363? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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