Sandbox escape in the Profile Backup component. This vulnerability was fixed in Firefox 150.0.3, Firefox ESR 115.36, Firefox ESR 140.11, and Thunderbird 140.11.
CVE-2026-8401
CRITICALNVD 9.89.8—
EchelonGraph scoreHIGH confidence
Score 9.8 from GitHub Security Advisory (severity: CRITICAL) published 2026-05-12. NVD baseline CVSS 9.8; sources differ by 0.0.
Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
9.8
- CVSS v3
- 9.8
- EG Score
- 9.8(high)
- EPSS
- 24.3%
- KEV
- Not listed
Published
May 12, 2026
Last Modified
May 19, 2026
References (5)
- security@mozillahttps://bugzilla.mozilla.org/show_bug.cgi?id=2038679
- 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/
Frequently asked(5)
What is CVE-2026-8401?
CVE-2026-8401 is a critical vulnerability published on May 12, 2026. Sandbox escape in the Profile Backup 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-2026-8401 disclosed?
CVE-2026-8401 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-2026-8401 actively exploited?
CVE-2026-8401 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 24.3% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-8401?
CVE-2026-8401 has a CVSS v3 base score of 9.8 (NVD).
How do I remediate CVE-2026-8401?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-8401, 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.
Dependency Blast Radius
See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-8401
Is Your Infrastructure Affected by CVE-2026-8401?
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