What is CVE-2026-8389?

CVE-2026-8389 is a high-severity vulnerability in Mozilla Firefox, classified under Improper Restriction of Operations within the Bounds of a Memory Buffer. CVSS score: 8.8/10. Published 2026-05-12.

How severe is CVE-2026-8389?

High severity. CVSS v3 base score is 8.8 out of 10.

Is CVE-2026-8389 known to be exploited?

1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

Buffer overflow in Mozilla Firefox

CVE-2026-8389

JIT miscompilation in the JavaScript Engine: JIT component. This vulnerability was fixed in Firefox 150.0.3.

Vulnerability class: Buffer Overflow

EPSS: 0.001 (17.0th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 8.8 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H.

Affected products

Mozilla Firefox — versions 150.0.3

Weakness classification (CWE)

Public proof-of-concept exploits

crixpwn/CVE-2026-8389

References

security@mozilla.org (Permissions Required)
security@mozilla.org (Vendor Advisory)
134c704f-9b21-4f2e-91b3-4a467353bcc0

Frequently asked questions

What is CVE-2026-8389?: CVE-2026-8389 is a high-severity vulnerability in Mozilla Firefox, classified under Improper Restriction of Operations within the Bounds of a Memory Buffer. CVSS score: 8.8/10. Published 2026-05-12.
How severe is CVE-2026-8389?: High severity. CVSS v3 base score is 8.8 out of 10.
Is CVE-2026-8389 known to be exploited?: 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.