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.

870vulnerabilities

253critical

616high

15exploited

8.7average CVSS score

Latest first

9.8 Critical severity
Firefox: Use After Free
CVE-2026-74943Aug 18, 2026Mozilla
Use-after-free in the Graphics: ImageLib 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.
8.8 High severity
Firefox: Improper Privilege Management
CVE-2026-74942Aug 18, 2026Mozilla
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.
8.8 High severity
Firefox: Improper Privilege Management
CVE-2026-74941Aug 18, 2026Mozilla
Privilege escalation in the Graphics: CanvasWebGL component. This vulnerability was fixed in Firefox 154, Firefox ESR 140.14, Firefox ESR 153.1, Thunderbird 154, Thunderbird 140.14, and Thunderbird 153.1.
9.8 Critical severity
Firefox: Use After Free
CVE-2026-74940Aug 18, 2026Mozilla
Use-after-free in the Graphics: Text 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.
8.8 High severity
Firefox: Improper Privilege Management
CVE-2026-74939Aug 18, 2026Mozilla
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.
9.1 Critical severity
Firefox: Protection Mechanism Failure
CVE-2026-74938Aug 18, 2026Mozilla
Mitigation bypass in the JavaScript: GC component. This vulnerability was fixed in Firefox 154, Firefox ESR 153.1, Thunderbird 154, and Thunderbird 153.1.
8.8 High severity
Firefox: Use After Free
CVE-2026-74937Aug 18, 2026Mozilla
Use-after-free in the JavaScript: GC component. This vulnerability was fixed in Firefox 154, Firefox ESR 153.1, Thunderbird 154, and Thunderbird 153.1.
9.8 Critical severity
Firefox: Use After Free
CVE-2026-74936Aug 18, 2026Mozilla
Use-after-free in the JavaScript: WebAssembly component. This vulnerability was fixed in Firefox 154, Firefox ESR 140.14, Firefox ESR 153.1, Thunderbird 154, Thunderbird 140.14, and Thunderbird 153.1.
8.8 High severity
Firefox: Improper Privilege Management
CVE-2026-74935Aug 18, 2026Mozilla
Privilege escalation in the DOM: Networking 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.
7.5 High severity
Firefox: Exposure of Sensitive Information to an Unauthorized Actor
CVE-2026-74934Aug 18, 2026Mozilla
Site isolation issue in the Graphics: CanvasWebGL 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.
9.8 Critical severity
Firefox: Improper Restriction of Operations within the Bounds of a Memory Buffer
CVE-2026-16412Jul 21, 2026Mozilla
Memory safety bugs present in Thunderbird ESR 140.12 and Thunderbird 152. 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
9.8 Critical severity
Firefox: Improper Restriction of Operations within the Bounds of a Memory Buffer
CVE-2026-16411Jul 21, 2026Mozilla
Memory safety bugs present in Thunderbird 152. 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 153 and Thunder
7.5 High severity
Firefox: Exposure of Sensitive Information to an Unauthorized Actor
CVE-2026-16405Jul 21, 2026Mozilla
Information disclosure in the Networking: WebSockets component. This vulnerability was fixed in Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13.
7.5 High severity
Firefox: Exposure of Sensitive Information to an Unauthorized Actor
CVE-2026-16391Jul 21, 2026Mozilla
Information disclosure in the Storage: IndexedDB component. This vulnerability was fixed in Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13.
9.1 Critical severity
Firefox: Protection Mechanism Failure
CVE-2026-16390Jul 21, 2026Mozilla
Mitigation bypass in the Enterprise Policies component. This vulnerability was fixed in Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13.
9.8 Critical severity
Firefox: Exposure of Sensitive Information to an Unauthorized Actor
CVE-2026-16387Jul 21, 2026Mozilla
Site isolation issue in the Networking component. This vulnerability was fixed in Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13.
7.5 High severity
Firefox: Use of Uninitialized Resource
CVE-2026-16386Jul 21, 2026Mozilla
Information disclosure due to uninitialized memory in the Graphics: WebGPU component. This vulnerability was fixed in Firefox 153 and Thunderbird 153.
7.5 High severity
Firefox: Use of Uninitialized Resource
CVE-2026-16385Jul 21, 2026Mozilla
Information disclosure due to uninitialized memory in the Graphics: WebGPU component. This vulnerability was fixed in Firefox 153 and Thunderbird 153.
7.5 High severity
Firefox: Use of Uninitialized Resource
CVE-2026-16384Jul 21, 2026Mozilla
Information disclosure due to uninitialized memory in the Graphics: WebGPU component. This vulnerability was fixed in Firefox 153 and Thunderbird 153.
9.8 Critical severity
Firefox: Protection Mechanism Failure
CVE-2026-16383Jul 21, 2026Mozilla
Mitigation bypass in the DOM: Networking component. This vulnerability was fixed in Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13.
9.1 Critical severity
Firefox: Origin Validation Error
CVE-2026-16381Jul 21, 2026Mozilla
Same-origin policy bypass in the Networking: DNS component. This vulnerability was fixed in Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13.
8.8 High severity
Firefox: Improper Privilege Management
CVE-2026-16379Jul 21, 2026Mozilla
Privilege escalation in the DOM: Content Processes component. This vulnerability was fixed in Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13.
9.8 Critical severity
Firefox: Protection Mechanism Failure
CVE-2026-16377Jul 21, 2026Mozilla
Mitigation bypass in the PDF Viewer component. This vulnerability was fixed in Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13.
9.8 Critical severity
Firefox: Origin Validation Error
CVE-2026-16375Jul 21, 2026Mozilla
Site isolation issue in the Networking: HTTP component. This vulnerability was fixed in Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13.
7.5 High severity
Firefox: Exposure of Sensitive Information to an Unauthorized Actor
CVE-2026-16374Jul 21, 2026Mozilla
Information disclosure in the Framework component in DevTools. This vulnerability was fixed in Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13.
8.8 High severity
Firefox: Improper Privilege Management
CVE-2026-16371Jul 21, 2026Mozilla
Privilege escalation in the DOM: Navigation component. This vulnerability was fixed in Firefox 153, Firefox ESR 140.13, Thunderbird 153, Thunderbird 140.13, Firefox ESR 140.15, and Thunderbird 140.15.
9.8 Critical severity
Firefox: Integer Overflow or Wraparound
CVE-2026-16369Jul 21, 2026Mozilla
Integer overflow in the JavaScript: WebAssembly component. This vulnerability was fixed in Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13.
9.8 Critical severity
Firefox: Improper Restriction of Operations within the Bounds of a Memory Buffer
CVE-2026-16368Jul 21, 2026Mozilla
Incorrect boundary conditions in the JavaScript: WebAssembly component. This vulnerability was fixed in Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13.
8.8 High severity
Firefox: Improper Privilege Management
CVE-2026-16365Jul 21, 2026Mozilla
Privilege escalation in the DOM: Workers component. This vulnerability was fixed in Firefox 153, Thunderbird 153, Firefox ESR 140.15, and Thunderbird 140.15.
9.8 Critical severity
Firefox: Incorrect Calculation
CVE-2026-16363Jul 21, 2026Mozilla
JIT miscompilation in the JavaScript: WebAssembly component. This vulnerability was fixed in Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13.
8.8 High severity
Firefox: Use After Free
CVE-2026-16362Jul 21, 2026Mozilla
Use-after-free in the WebRTC: Audio/Video component. This vulnerability was fixed in Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13.
9.8 Critical severity
Firefox: Improper Restriction of Operations within the Bounds of a Memory Buffer
CVE-2026-16361Jul 21, 2026Mozilla
Memory safety bugs present in Thunderbird ESR 140.12. 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 ESR 115.
9.8 Critical severity
Firefox: Improper Restriction of Operations within the Bounds of a Memory Buffer
CVE-2026-16360Jul 21, 2026Mozilla
Memory safety bugs present in Thunderbird ESR 140.12 and Thunderbird 152. 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
9.1 Critical severity
Firefox: Improper Restriction of Operations within the Bounds of a Memory Buffer
CVE-2026-16359Jul 21, 2026Mozilla
Incorrect boundary conditions in the Audio/Video: GMP component. This vulnerability was fixed in Firefox 153, Firefox ESR 115.38, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13.
9.8 Critical severity
Firefox: Origin Validation Error
CVE-2026-16358Jul 21, 2026Mozilla
Site isolation issue in the Graphics: WebRender component. This vulnerability was fixed in Firefox 153, Firefox ESR 115.38, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13.
9.8 Critical severity
Firefox: Improper Restriction of Operations within the Bounds of a Memory Buffer
CVE-2026-16357Jul 21, 2026Mozilla
Incorrect boundary conditions in the Graphics component. This vulnerability was fixed in Firefox 153, Firefox ESR 115.38, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13.
9.8 Critical severity
Firefox: Use After Free
CVE-2026-16356Jul 21, 2026Mozilla
Sandbox escape due to use-after-free in the Disability Access APIs component. This vulnerability was fixed in Firefox 153, Firefox ESR 115.38, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13.
9.8 Critical severity
Firefox: Access of Resource Using Incompatible Type
CVE-2026-16355Jul 21, 2026Mozilla
JIT miscompilation in the JavaScript Engine: JIT component. This vulnerability was fixed in Firefox 153, Firefox ESR 115.38, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13.
7.5 High severity
Firefox: Exposure of Sensitive Information to an Unauthorized Actor
CVE-2026-16354Jul 21, 2026Mozilla
Information disclosure in the Graphics: ImageLib component. This vulnerability was fixed in Firefox 153, Firefox ESR 115.38, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13.
9.8 Critical severity
Firefox: Use After Free
CVE-2026-16353Jul 21, 2026Mozilla
Invalid pointer in the DOM: Bindings (WebIDL) component. This vulnerability was fixed in Firefox 153, Firefox ESR 115.38, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13.