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CVE-2026-7321: Sandbox escape due to incorrect boundary conditions in the WebRTC: Networking 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: 2026-04-28 · updated 2026-10-26
• Weakness: CWE-120

Description

Sandbox escape due to incorrect boundary conditions in the WebRTC: Networking component. This vulnerability was fixed in Firefox 150, Thunderbird 150, Firefox ESR 140.10.1, and Thunderbird 140.10.1.

Affected products

• Mozilla Firefox: before 140.10.1; before 150.0 — fixed in 140.10.1, 150.0
• Mozilla Thunderbird: before 140.10.1; before 150.0 — fixed in 140.10.1, 150.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 140.10.1, 150.0; Mozilla Thunderbird 140.10.1, 150.0. Check the vendor advisory for mitigations.

References

• https://bugzilla.mozilla.org/show_bug.cgi?id=2029461
• https://www.mozilla.org/security/advisories/mfsa2026-30/
• https://www.mozilla.org/security/advisories/mfsa2026-33/
• https://www.mozilla.org/security/advisories/mfsa2026-36/
• https://www.mozilla.org/security/advisories/mfsa2026-39/

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