What’s Vulnerable › Vulnerabilities

CVE-2026-74942: Privilege escalation in the Remote Settings Client component

• Severity: high (CVSS 8.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-18 · updated 2026-08-21
• Weakness: CWE-269

Description

Privilege escalation in the Remote Settings Client component. This vulnerability was fixed in Firefox 154, Firefox ESR 115.39, Firefox ESR 140.14, Firefox ESR 153.1, Thunderbird 154, Thunderbird 140.14, and Thunderbird 153.1.

Affected products

• Mozilla Firefox: before 115.39.0; from 116.0 before 140.14.0; from 141.0 before 153.1.0 — fixed in 115.39.0, 140.14.0, 153.1.0
• Mozilla Thunderbird: before 140.14.0; from 141.0 before 153.1.0 — fixed in 140.14.0, 153.1.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 115.39.0, 140.14.0, 153.1.0; Mozilla Thunderbird 140.14.0, 153.1.0. Check the vendor advisory for mitigations.

References

• https://bugzilla.mozilla.org/show_bug.cgi?id=2056571
• https://www.mozilla.org/security/advisories/mfsa2026-74/
• https://www.mozilla.org/security/advisories/mfsa2026-75/
• https://www.mozilla.org/security/advisories/mfsa2026-76/
• https://www.mozilla.org/security/advisories/mfsa2026-77/
• https://www.mozilla.org/security/advisories/mfsa2026-78/
• https://www.mozilla.org/security/advisories/mfsa2026-79/
• https://www.mozilla.org/security/advisories/mfsa2026-80/

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