CVE-2026-0877
HighCVSS 8.1Exploitation Probability (EPSS)
Low risk34th percentile - higher than 34% of all known CVEs
Summary
This vulnerability allows bypassing security mechanisms in the DOM component of Firefox and Thunderbird. The flaw is fixed in Firefox 147, Firefox ESR 115.32, Firefox ESR 140.7, Thunderbird 147, and Thunderbird 140.7.
Risk Assessment
An attacker could exploit this flaw to bypass browser security controls, potentially leading to unauthorized data access or execution of malicious operations in the user's context.
Recommendation
Immediately update Firefox to version 147 or later and Thunderbird to version 147 or 140.7 depending on the ESR branch used.
Other vulnerabilities in Firefox
See all- CVE-2026-75874Critical
Sandbox escape in the Remote Settings Client component. This vulnerability was fixed in Firefox 154 and Thunderbird 154.
- CVE-2026-74990Critical
Internally found bugs in Firefox ESR 115.38, Firefox ESR 140.13, Firefox ESR 153.0 and Firefox 153. Some of these bugs showed evidence of memory corruption or another security-relevant defect and we presume that with enough effort some of these could have been exploited. 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.
- CVE-2026-74989Critical
Internally found bugs in Firefox 153. Some of these bugs showed evidence of memory corruption or another security-relevant defect and we presume that with enough effort some of these could have been exploited. This vulnerability was fixed in Firefox 154 and Thunderbird 154.
- CVE-2026-74988Critical
Internally found bugs in Firefox ESR 153.0 and Firefox 153. Some of these bugs showed evidence of memory corruption or another security-relevant defect and we presume that with enough effort some of these could have been exploited. This vulnerability was fixed in Firefox 154, Firefox ESR 153.1, Thunderbird 154, and Thunderbird 153.1.
- CVE-2026-74987Critical
Internally found bugs in Firefox ESR 140.13, Firefox ESR 153.0 and Firefox 153. Some of these bugs showed evidence of memory corruption or another security-relevant defect and we presume that with enough effort some of these could have been exploited. This vulnerability was fixed in Firefox 154, Firefox ESR 140.14, Firefox ESR 153.1, Thunderbird 154, Thunderbird 140.14, and Thunderbird 153.1.
- CVE-2026-74986Critical
Site isolation issue in the CSS Parsing and Computation component. This vulnerability was fixed in Firefox 154, Firefox ESR 153.1, Thunderbird 154, and Thunderbird 153.1.
- CVE-2026-74985Critical
Privilege escalation in the Enterprise Policies component. This vulnerability was fixed in Firefox 154, Firefox ESR 153.1, Thunderbird 154, and Thunderbird 153.1.
- CVE-2026-74979Critical
Mitigation bypass in the Add-ons Manager component. This vulnerability was fixed in Firefox 154, Firefox ESR 153.1, Thunderbird 154, and Thunderbird 153.1.
- CVE-2026-74964Critical
Integer overflow in the Graphics component. Fixed in Firefox 154, Firefox ESR 140.14, Firefox ESR 153.1, Thunderbird 154, Thunderbird 140.14, and Thunderbird 153.1.
- CVE-2026-74961Critical
Side-channel vulnerability in the Web Audio component. Fixed in Firefox 154, Firefox ESR 153.1, Thunderbird 154, and Thunderbird 153.1.
Original NVD description (English source)
Mitigation bypass in the DOM: Security component. This vulnerability was fixed in Firefox 147, Firefox ESR 115.32, Firefox ESR 140.7, Thunderbird 147, and Thunderbird 140.7.