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: Exposure of Sensitive Information to an Unauthorized Actor

  CVE-2026-4712Mar 24, 2026Mozilla

  Information disclosure in the Widget: Cocoa component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

• 9.8 Critical severity

  Firefox: Use After Free

  CVE-2026-4711Mar 24, 2026Mozilla

  Use-after-free in the Widget: Cocoa component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

• 9.8 Critical severity

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

  CVE-2026-4710Mar 24, 2026Mozilla

  Incorrect boundary conditions in the Audio/Video component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

• 7.5 High severity

  Firefox: Improper Check for Unusual or Exceptional Conditions

  CVE-2026-4709Mar 24, 2026Mozilla

  Incorrect boundary conditions in the Audio/Video: GMP component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

• 7.5 High severity

  Firefox: Improper Check for Unusual or Exceptional Conditions

  CVE-2026-4708Mar 24, 2026Mozilla

  Incorrect boundary conditions in the Graphics component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

• 7.5 High severity

  Firefox: Improper Check for Unusual or Exceptional Conditions

  CVE-2026-4707Mar 24, 2026Mozilla

  Incorrect boundary conditions in the Graphics: Canvas2D component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

• 7.5 High severity

  Firefox: Improper Check for Unusual or Exceptional Conditions

  CVE-2026-4706Mar 24, 2026Mozilla

  Incorrect boundary conditions in the Graphics: Canvas2D component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

• 9.8 Critical severity

  Firefox: Reliance on Undefined, Unspecified, or Implementation-Defined Behavior

  CVE-2026-4705Mar 24, 2026Mozilla

  Undefined behavior in the WebRTC: Signaling component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

• 7.5 High severity

  Firefox: Uncontrolled Resource Consumption

  CVE-2026-4704Mar 24, 2026Mozilla

  Denial-of-service in the WebRTC: Signaling component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

• 9.8 Critical severity

  Firefox: Access of Resource Using Incompatible Type

  CVE-2026-4702Mar 24, 2026Mozilla

  JIT miscompilation in the JavaScript Engine component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

• 9.8 Critical severity

  Firefox: Use After Free

  CVE-2026-4701Mar 24, 2026Mozilla

  Use-after-free in the JavaScript Engine component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

• 9.8 Critical severity

  Firefox: Authentication Bypass Using an Alternate Path or Channel

  CVE-2026-4700Mar 24, 2026Mozilla

  Mitigation bypass in the Networking: HTTP component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

• 7.5 High severity

  Firefox: Improper Check for Unusual or Exceptional Conditions

  CVE-2026-4699Mar 24, 2026Mozilla

  Incorrect boundary conditions in the Layout: Text and Fonts component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

• 9.8 Critical severity

  Firefox: Access of Resource Using Incompatible Type

  CVE-2026-4698Mar 24, 2026Mozilla

  JIT miscompilation in the JavaScript Engine: JIT component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

• 7.5 High severity

  Firefox: Improper Check for Unusual or Exceptional Conditions

  CVE-2026-4697Mar 24, 2026Mozilla

  Incorrect boundary conditions in the Audio/Video: Web Codecs component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

• 9.8 Critical severity

  Firefox: Use After Free

  CVE-2026-4696Mar 24, 2026Mozilla

  Use-after-free in the Layout: Text and Fonts component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

• 7.5 High severity

  Firefox: Improper Check for Unusual or Exceptional Conditions

  CVE-2026-4695Mar 24, 2026Mozilla

  Incorrect boundary conditions in the Audio/Video: Web Codecs component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

• 7.5 High severity

  Firefox: Integer Overflow or Wraparound

  CVE-2026-4694Mar 24, 2026Mozilla

  Incorrect boundary conditions, integer overflow in the Graphics component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

• 7.5 High severity

  Firefox: Improper Check for Unusual or Exceptional Conditions

  CVE-2026-4693Mar 24, 2026Mozilla

  Incorrect boundary conditions in the Audio/Video: Playback component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

• 10.0 Critical severity

  Firefox: Improper Isolation or Compartmentalization

  CVE-2026-4692Mar 24, 2026Mozilla

  Sandbox escape in the Responsive Design Mode component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

• 9.8 Critical severity

  Firefox: Use After Free

  CVE-2026-4691Mar 24, 2026Mozilla

  Use-after-free in the CSS Parsing and Computation component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

• 8.6 High severity

  Firefox: Integer Overflow or Wraparound

  CVE-2026-4690Mar 24, 2026Mozilla

  Sandbox escape due to incorrect boundary conditions, integer overflow in the XPCOM component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

• 10.0 Critical severity

  Firefox: Integer Overflow or Wraparound

  CVE-2026-4689Mar 24, 2026Mozilla

  Sandbox escape due to incorrect boundary conditions, integer overflow in the XPCOM component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

• 10.0 Critical severity

  Firefox: Use After Free

  CVE-2026-4688Mar 24, 2026Mozilla

  Sandbox escape due to use-after-free in the Disability Access APIs component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

• 8.6 High severity

  Firefox: Improper Check for Unusual or Exceptional Conditions

  CVE-2026-4687Mar 24, 2026Mozilla

  Sandbox escape due to incorrect boundary conditions in the Telemetry component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

• 7.5 High severity

  Firefox: Improper Check for Unusual or Exceptional Conditions

  CVE-2026-4686Mar 24, 2026Mozilla

  Incorrect boundary conditions in the Graphics: Canvas2D component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

• 7.5 High severity

  Firefox: Improper Check for Unusual or Exceptional Conditions

  CVE-2026-4685Mar 24, 2026Mozilla

  Incorrect boundary conditions in the Graphics: Canvas2D component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

• 7.5 High severity

  Firefox: Concurrent Execution using Shared Resource with Improper Synchronization

  CVE-2026-4684Mar 24, 2026Mozilla

  Race condition, use-after-free in the Graphics: WebRender component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

• 8.8 High severity

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

  CVE-2026-3847Mar 10, 2026Mozilla

  Memory safety bugs present in Firefox 148.0.2. 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 148.0.2.

• 9.8 Critical severity

  Firefox: Out-of-bounds Write

  CVE-2026-2807Feb 24, 2026Mozilla

  Memory safety bugs present in Firefox 147 and Thunderbird 147. 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

• 9.8 Critical severity

  Firefox: Out-of-bounds Write

  CVE-2026-2793Feb 24, 2026Mozilla

  Memory safety bugs present in Firefox ESR 115.32, Firefox ESR 140.7, Thunderbird ESR 140.7, Firefox 147 and Thunderbird 147. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited

• 9.8 Critical severity

  Firefox: Out-of-bounds Write

  CVE-2026-2792Feb 24, 2026Mozilla

  Memory safety bugs present in Firefox ESR 140.7, Thunderbird ESR 140.7, Firefox 147 and Thunderbird 147. 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: Authentication Bypass Using an Alternate Path or Channel

  CVE-2026-2791Feb 24, 2026Mozilla

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

• 9.8 Critical severity

  Firefox: Origin Validation Error

  CVE-2026-2790Feb 24, 2026Mozilla

  Same-origin policy bypass in the Networking: JAR 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-2026-2789Feb 24, 2026Mozilla

  Use-after-free 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: Improper Restriction of Operations within the Bounds of a Memory Buffer

  CVE-2026-2788Feb 24, 2026Mozilla

  Incorrect boundary conditions in the Audio/Video: GMP 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-2026-2787Feb 24, 2026Mozilla

  Use-after-free in the DOM: Window and Location 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-2026-2786Feb 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: Access of Uninitialized Pointer

  CVE-2026-2785Feb 24, 2026Mozilla

  Invalid pointer 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: Authentication Bypass Using an Alternate Path or Channel

  CVE-2026-2784Feb 24, 2026Mozilla

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