CVE-2026-2791: Mitigation bypass in the Networking: Cache component

Severity: critical (CVSS 9.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.6% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-02-24 · updated 2026-06-17
Weakness: CWE-288

Description

Mitigation bypass in the Networking: Cache component. This vulnerability was fixed in Firefox 148, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

Affected products

Mozilla Firefox: before 140.8.0; before 148.0 — fixed in 140.8.0, 148.0
Mozilla Thunderbird: before 140.8.0; before 148.0 — fixed in 140.8.0, 148.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 140.8.0, 148.0; Mozilla Thunderbird 140.8.0, 148.0. Check the vendor advisory for mitigations.

References

https://bugzilla.mozilla.org/show_bug.cgi?id=2015220
https://www.mozilla.org/security/advisories/mfsa2026-13/
https://www.mozilla.org/security/advisories/mfsa2026-15/
https://www.mozilla.org/security/advisories/mfsa2026-16/
https://www.mozilla.org/security/advisories/mfsa2026-17/

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