CVE-2025-4083

CRITICAL 9.1

Process isolation bypass using "javascript:" URI links in cross-origin frames

CVSS Score

9.1

EPSS Score

0.0%

EPSS Percentile

0th

A process isolation vulnerability in Thunderbird stemmed from improper handling of javascript: URIs, which could allow content to execute in the top-level document's process instead of the intended frame, potentially enabling a sandbox escape. This vulnerability was fixed in Firefox 138, Firefox ESR 128.10, Firefox ESR 115.23, Thunderbird 138, and Thunderbird 128.10.

Vendor	mozilla
Product	firefox
Ecosystems	Browser JavaScript
Industries	Technology
Published	Apr 29, 2025
Last Updated	Apr 13, 2026

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Affected Versions

Mozilla / Firefox

All versions affected

Mozilla / Thunderbird

All versions affected

References

NVD ↗ CVE.org ↗ EPSS Data ↗

bugzilla.mozilla.org: https://bugzilla.mozilla.org/show_bug.cgi?id=1958350 mozilla.org: https://www.mozilla.org/security/advisories/mfsa2025-28/ mozilla.org: https://www.mozilla.org/security/advisories/mfsa2025-29/ mozilla.org: https://www.mozilla.org/security/advisories/mfsa2025-30/ mozilla.org: https://www.mozilla.org/security/advisories/mfsa2025-31/ mozilla.org: https://www.mozilla.org/security/advisories/mfsa2025-32/ lists.debian.org: https://lists.debian.org/debian-lts-announce/2025/05/msg00024.html

Credits

Nika Layzell