What’s Vulnerable › Vulnerabilities

CVE-2026-100804: Sandbox escape due to use-after-free in the Preferences: Backend component

• Severity: critical (CVSS 9.6 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-29 · updated 2026-10-19
• Weakness: CWE-416

Description

Sandbox escape due to use-after-free in the Preferences: Backend component. This vulnerability was fixed in Thunderbird 157 and Firefox 157.

Affected products

• Mozilla Firefox: before 157.0.0 — fixed in 157.0.0
• Mozilla Thunderbird: before 157.0 — fixed in 157.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 157.0.0; Mozilla Thunderbird 157.0. Check the vendor advisory for mitigations.

References

• https://bugzilla.mozilla.org/show_bug.cgi?id=2058647
• https://www.mozilla.org/security/advisories/mfsa2026-101/
• https://www.mozilla.org/security/advisories/mfsa2026-97/

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