CVE-2026-8391

MEDIUMNVD 5.35.3—

5.3

Other issue in the JavaScript Engine component. This vulnerability was fixed in Firefox 150.0.3, Firefox ESR 115.36, Firefox ESR 140.11, and Thunderbird 140.11.

CVSS v3: 5.3
EG Score: 5.3(high)
EPSS: 28.8%
KEV: Not listed

Published

May 12, 2026

Last Modified

May 19, 2026

References (5)

security@mozillahttps://bugzilla.mozilla.org/show_bug.cgi?id=2038575
security@mozillahttps://www.mozilla.org/security/advisories/mfsa2026-45/
security@mozillahttps://www.mozilla.org/security/advisories/mfsa2026-47/
security@mozillahttps://www.mozilla.org/security/advisories/mfsa2026-48/
security@mozillahttps://www.mozilla.org/security/advisories/mfsa2026-51/

Vendor Advisories for CVE-2026-8391(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

GHSA-93pv-vhrf-wv64
GitHub Security AdvisoriesMedium
Other issue in the JavaScript Engine component. This vulnerability was fixed in Firefox 150.0.3.

Frequently asked(5)

What is CVE-2026-8391?

CVE-2026-8391 is a medium vulnerability published on May 12, 2026. Other issue in the JavaScript Engine component. This vulnerability was fixed in Firefox 150.0.3, Firefox ESR 115.36, Firefox ESR 140.11, and Thunderbird 140.11.

When was CVE-2026-8391 disclosed?

CVE-2026-8391 was first published in the National Vulnerability Database on May 12, 2026, with the most recent update on May 19, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.

Is CVE-2026-8391 actively exploited?

CVE-2026-8391 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 28.8% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.

What is the CVSS score of CVE-2026-8391?

CVE-2026-8391 has a CVSS v3 base score of 5.3 (NVD).

How do I remediate CVE-2026-8391?

Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-8391, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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CVE-2026-8391

📅 Published

🔄 Last Modified

🔗 References (5)

📣 Vendor Advisories for CVE-2026-8391(1)

❓ Frequently asked(5)