Firefox vulnerabilities

870 known vulnerabilities in Firefox from Mozilla. 869 are rated high or critical, and 15 have been exploited in real attacks. Each entry lists the affected versions and the release that fixes it, where the vendor has published one.

Latest first

• 7.5 High severity

  Firefox: Access of Resource Using Incompatible Type

  CVE-2026-2783Feb 24, 2026Mozilla

  Information disclosure due to JIT miscompilation in the JavaScript Engine: JIT component. This vulnerability was fixed in Firefox 148, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

• 9.8 Critical severity

  Firefox: Improper Privilege Management

  CVE-2026-2782Feb 24, 2026Mozilla

  Privilege escalation in the Netmonitor component. This vulnerability was fixed in Firefox 148, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

• 9.8 Critical severity

  Firefox: Integer Overflow or Wraparound

  CVE-2026-2781Feb 24, 2026Mozilla

  Integer overflow in the Libraries component in NSS. This vulnerability was fixed in Firefox 148, Firefox ESR 140.8, Thunderbird 148, Thunderbird 140.8, and Firefox ESR 115.35.

• 9.8 Critical severity

  Firefox: Improper Privilege Management

  CVE-2026-2780Feb 24, 2026Mozilla

  Privilege escalation in the Netmonitor component. This vulnerability was fixed in Firefox 148, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

• 9.8 Critical severity

  Firefox: Improper Restriction of Operations within the Bounds of a Memory Buffer

  CVE-2026-2779Feb 24, 2026Mozilla

  Incorrect boundary conditions in the Networking: JAR component. This vulnerability was fixed in Firefox 148, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

• 10.0 Critical severity

  Firefox: Improper Restriction of Operations within the Bounds of a Memory Buffer

  CVE-2026-2778Feb 24, 2026Mozilla

  Sandbox escape due to incorrect boundary conditions in the DOM: Core & HTML component. This vulnerability was fixed in Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

• 9.8 Critical severity

  Firefox: Improper Privilege Management

  CVE-2026-2777Feb 24, 2026Mozilla

  Privilege escalation in the Messaging System component. This vulnerability was fixed in Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

• 10.0 Critical severity

  Firefox: Improper Restriction of Operations within the Bounds of a Memory Buffer

  CVE-2026-2776Feb 24, 2026Mozilla

  Sandbox escape due to incorrect boundary conditions in the Telemetry component in External Software. This vulnerability was fixed in Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

• 9.8 Critical severity

  Firefox: Authentication Bypass Using an Alternate Path or Channel

  CVE-2026-2775Feb 24, 2026Mozilla

  Mitigation bypass in the DOM: HTML Parser component. This vulnerability was fixed in Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

• 9.8 Critical severity

  Firefox: Integer Overflow or Wraparound

  CVE-2026-2774Feb 24, 2026Mozilla

  Integer overflow in the Audio/Video component. This vulnerability was fixed in Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

• 9.8 Critical severity

  Firefox: Improper Restriction of Operations within the Bounds of a Memory Buffer

  CVE-2026-2773Feb 24, 2026Mozilla

  Incorrect boundary conditions in the Web Audio component. This vulnerability was fixed in Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

• 9.8 Critical severity

  Firefox: Use After Free

  CVE-2026-2772Feb 24, 2026Mozilla

  Use-after-free in the Audio/Video: Playback component. This vulnerability was fixed in Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

• 9.8 Critical severity

  Firefox: Out-of-bounds Read

  CVE-2026-2771Feb 24, 2026Mozilla

  Undefined behavior in the DOM: Core & HTML component. This vulnerability was fixed in Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

• 9.8 Critical severity

  Firefox: Use After Free

  CVE-2026-2770Feb 24, 2026Mozilla

  Use-after-free in the DOM: Bindings (WebIDL) component. This vulnerability was fixed in Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

• 7.5 High severity

  Firefox: Use After Free

  CVE-2026-2769Feb 24, 2026Mozilla

  Use-after-free in the Storage: IndexedDB component. This vulnerability was fixed in Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

• 10.0 Critical severity

  Firefox: Improper Access Control

  CVE-2026-2768Feb 24, 2026Mozilla

  Sandbox escape in the Storage: IndexedDB component. This vulnerability was fixed in Firefox 148, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

• 9.8 Critical severity

  Firefox: Use After Free

  CVE-2026-2767Feb 24, 2026Mozilla

  Use-after-free in the JavaScript: WebAssembly component. This vulnerability was fixed in Firefox 148, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

• 9.8 Critical severity

  Firefox: Use After Free

  CVE-2026-2766Feb 24, 2026Mozilla

  Use-after-free in the JavaScript Engine: JIT component. This vulnerability was fixed in Firefox 148, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

• 9.8 Critical severity

  Firefox: Use After Free

  CVE-2026-2765Feb 24, 2026Mozilla

  Use-after-free in the JavaScript Engine component. This vulnerability was fixed in Firefox 148, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

• 9.8 Critical severity

  Firefox: Use After Free

  CVE-2026-2764Feb 24, 2026Mozilla

  JIT miscompilation, use-after-free in the JavaScript Engine: JIT component. This vulnerability was fixed in Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

• 9.8 Critical severity

  Firefox: Use After Free

  CVE-2026-2763Feb 24, 2026Mozilla

  Use-after-free in the JavaScript Engine component. This vulnerability was fixed in Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

• 9.8 Critical severity

  Firefox: Integer Overflow or Wraparound

  CVE-2026-2762Feb 24, 2026Mozilla

  Integer overflow in the JavaScript: Standard Library component. This vulnerability was fixed in Firefox 148, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

• 10.0 Critical severity

  Firefox: Protection Mechanism Failure

  CVE-2026-2761Feb 24, 2026Mozilla

  Sandbox escape in the Graphics: WebRender component. This vulnerability was fixed in Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

• 10.0 Critical severity

  Firefox: Improper Handling of Physical or Environmental Conditions

  CVE-2026-2760Feb 24, 2026Mozilla

  Sandbox escape due to incorrect boundary conditions in the Graphics: WebRender component. This vulnerability was fixed in Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

• 9.8 Critical severity

  Firefox: Improper Handling of Physical or Environmental Conditions

  CVE-2026-2759Feb 24, 2026Mozilla

  Incorrect boundary conditions in the Graphics: ImageLib component. This vulnerability was fixed in Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

• 9.8 Critical severity

  Firefox: Use After Free

  CVE-2026-2758Feb 24, 2026Mozilla

  Use-after-free in the JavaScript: GC component. This vulnerability was fixed in Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

• 9.8 Critical severity

  Firefox: Improper Handling of Physical or Environmental Conditions

  CVE-2026-2757Feb 24, 2026Mozilla

  Incorrect boundary conditions in the WebRTC: Audio/Video component. This vulnerability was fixed in Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

• 9.8 Critical severity

  Firefox for iOS: User Interface (UI) Misrepresentation of Critical Information

  CVE-2026-2634Feb 24, 2026Mozilla

  Malicious scripts could cause desynchronization between the address bar and web content before a response is received in Firefox iOS, allowing attacker-controlled pages to be presented under spoofed domains. This vulnerability was fixed in Firefox for iOS 147.

• 7.5 High severity

  Firefox: Heap-based Buffer Overflow

  CVE-2026-2447Feb 16, 2026Mozilla

  Heap buffer overflow in libvpx. This vulnerability was fixed in Firefox 147.0.4, Firefox ESR 140.7.1, Firefox ESR 115.32.1, Thunderbird 140.7.2, and Thunderbird 147.0.2.

• 9.8 Critical severity

  Firefox: Improper Restriction of Operations within the Bounds of a Memory Buffer

  CVE-2026-0892Jan 13, 2026Mozilla

  Memory safety bugs present in Firefox 146 and Thunderbird 146. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox

• 7.5 High severity

  Firefox: Improper Restriction of Operations within the Bounds of a Memory Buffer

  CVE-2026-0891Jan 13, 2026Mozilla

  Memory safety bugs present in Firefox ESR 140.6, Thunderbird ESR 140.6, Firefox 146 and Thunderbird 146. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary cod

• 9.8 Critical severity

  Firefox: Use After Free

  CVE-2026-0884Jan 13, 2026Mozilla

  Use-after-free in the JavaScript Engine component. This vulnerability was fixed in Firefox 147, Firefox ESR 140.7, Thunderbird 147, and Thunderbird 140.7.

• 7.5 High severity

  Firefox: Use After Free

  CVE-2026-0882Jan 13, 2026Mozilla

  Use-after-free in the IPC component. This vulnerability was fixed in Firefox 147, Firefox ESR 115.32, Firefox ESR 140.7, Thunderbird 147, and Thunderbird 140.7.

• 7.5 High severity

  Firefox: Integer Overflow or Wraparound

  CVE-2026-0880Jan 13, 2026Mozilla

  Sandbox escape due to integer overflow in the Graphics component. This vulnerability was fixed in Firefox 147, Firefox ESR 115.32, Firefox ESR 140.7, Thunderbird 147, and Thunderbird 140.7.

• 7.5 High severity

  Firefox: Improper Restriction of Operations within the Bounds of a Memory Buffer

  CVE-2026-0879Jan 13, 2026Mozilla

  Sandbox escape due to incorrect boundary conditions in the Graphics component. This vulnerability was fixed in Firefox 147, Firefox ESR 115.32, Firefox ESR 140.7, Thunderbird 147, and Thunderbird 140.7.

• 7.5 High severity

  Sandbox escape due to incorrect boundary conditions in the Graphics: CanvasWebGL component.

  CVE-2026-0878Jan 13, 2026Mozilla

  Sandbox escape due to incorrect boundary conditions in the Graphics: CanvasWebGL component. This vulnerability was fixed in Firefox 147, Firefox ESR 140.7, Thunderbird 147, and Thunderbird 140.7.

• 7.5 High severity

  Firefox: Protection Mechanism Failure

  CVE-2026-0877Jan 13, 2026Mozilla

  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.

• 8.8 High severity

  Firefox: Improper Restriction of Operations within the Bounds of a Memory Buffer

  CVE-2025-14861Dec 18, 2025Mozilla

  Memory safety bugs present in Firefox 146. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox 146.0.1.

• 8.1 High severity

  Firefox: Out-of-bounds Write

  CVE-2025-14333Dec 9, 2025Mozilla

  Memory safety bugs present in Firefox ESR 140.5, Thunderbird ESR 140.5, Firefox 145 and Thunderbird 145. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary cod

• 7.3 High severity

  Firefox: Out-of-bounds Write

  CVE-2025-14332Dec 9, 2025Mozilla

  Memory safety bugs present in Firefox 145 and Thunderbird 145. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox