What’s Vulnerable › Vulnerabilities

CVE-2026-74939: Privilege escalation in the DOM: Navigation 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 DOM: Navigation 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=2054416
• 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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