Mozilla Firefox Open source web browser
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Recent Mozilla Firefox Security Advisories
| Advisory | Title | Published |
|---|---|---|
| mfsa2026-82 | Security Vulnerabilities fixed in Firefox 155 mfsa2026-82 | September 1, 2026 |
| mfsa2026-83 | Security Vulnerabilities fixed in Firefox ESR 115.40 mfsa2026-83 | September 1, 2026 |
| mfsa2026-84 | Security Vulnerabilities fixed in Firefox ESR 140.15 mfsa2026-84 | September 1, 2026 |
| mfsa2026-85 | Security Vulnerabilities fixed in Firefox ESR 153.2 mfsa2026-85 | September 1, 2026 |
| mfsa2026-81 | Security Vulnerabilities fixed in Firefox for iOS 155.0 mfsa2026-81 | August 31, 2026 |
| mfsa2026-74 | Security Vulnerabilities fixed in Firefox 154 mfsa2026-74 | August 18, 2026 |
| mfsa2026-75 | Security Vulnerabilities fixed in Firefox ESR 115.39 mfsa2026-75 | August 18, 2026 |
| mfsa2026-77 | Security Vulnerabilities fixed in Firefox ESR 153.1 mfsa2026-77 | August 18, 2026 |
| mfsa2026-76 | Security Vulnerabilities fixed in Firefox ESR 140.14 mfsa2026-76 | August 18, 2026 |
| mfsa2026-73 | Security Vulnerabilities fixed in Firefox for Android 153.0.3 mfsa2026-73 | August 4, 2026 |
Known Exploited Mozilla Firefox Vulnerabilities
The following Mozilla Firefox vulnerabilities have been marked by CISA as Known to be Exploited by threat actors.
| Title | Description | Added |
|---|---|---|
| Mozilla Firefox Use-After-Free Vulnerability |
Mozilla Firefox and Firefox ESR contain a use-after-free vulnerability in Animation timelines that allows for code execution in the content process. CVE-2024-9680 Exploit Probability: 23.2% |
October 15, 2024 |
| Mozilla Firefox Security Feature Bypass Vulnerability |
Moxilla Firefox allows remote attackers to bypass the Same Origin Policy to read arbitrary files or gain privileges. CVE-2015-4495 Exploit Probability: 71.4% |
May 25, 2022 |
| Mozilla Firefox Use-After-Free Vulnerability |
Mozilla Firefox contains a use-after-free vulnerability in WebGPU IPC Framework which can be exploited to perform arbitrary code execution. CVE-2022-26486 Exploit Probability: 2.3% |
March 7, 2022 |
| Mozilla Firefox Use-After-Free Vulnerability |
Mozilla Firefox contains a use-after-free vulnerability in XSLT parameter processing which can be exploited to perform arbitrary code execution. CVE-2022-26485 Exploit Probability: 13.8% |
March 7, 2022 |
| Mozilla Firefox Information Disclosure Vulnerability |
Mozilla Firefox does not properly initialize data structures for the nsDOMSVGZoomEvent::mPreviousScale and nsDOMSVGZoomEvent::mNewScale functions, which allows remote attackers to obtain sensitive information from process memory via a crafted web site. CVE-2013-1675 Exploit Probability: 6.7% |
March 3, 2022 |
The vulnerability CVE-2015-4495: Mozilla Firefox Security Feature Bypass Vulnerability is in the top 1% of the currently known exploitable vulnerabilities. 2 known exploited Mozilla Firefox vulnerabilities are in the top 5% (95th percentile or greater) of the EPSS exploit probability rankings.
EOL Dates
Ensure that you are using a supported version of Mozilla Firefox. Here are some end of life, and end of support dates for Mozilla Firefox.
| Release | EOL Date | Status |
|---|---|---|
| 155 | - |
Active
|
| 154 | September 1, 2026 |
EOL
Mozilla Firefox 154 became EOL in 2026. |
| 153 | - |
Active
|
| 152 | July 21, 2026 |
EOL
Mozilla Firefox 152 became EOL in 2026. |
| 151 | June 16, 2026 |
EOL
Mozilla Firefox 151 became EOL in 2026. |
| 150 | May 18, 2026 |
EOL
Mozilla Firefox 150 became EOL in 2026. |
| 149 | April 21, 2026 |
EOL
Mozilla Firefox 149 became EOL in 2026. |
| 148 | March 24, 2026 |
EOL
Mozilla Firefox 148 became EOL in 2026. |
| 147 | February 24, 2026 |
EOL
Mozilla Firefox 147 became EOL in 2026. |
| 146 | January 13, 2026 |
EOL
Mozilla Firefox 146 became EOL in 2026. |
| 145 | December 9, 2025 |
EOL
Mozilla Firefox 145 became EOL in 2025. |
| 144 | November 11, 2025 |
EOL
Mozilla Firefox 144 became EOL in 2025. |
| 143 | October 14, 2025 |
EOL
Mozilla Firefox 143 became EOL in 2025. |
| 142 | September 16, 2025 |
EOL
Mozilla Firefox 142 became EOL in 2025. |
| 141 | August 19, 2025 |
EOL
Mozilla Firefox 141 became EOL in 2025. |
| 140 | September 29, 2026 |
EOL This Year
Mozilla Firefox 140 will become EOL this year, in September 2026. |
| 139 | June 24, 2025 |
EOL
Mozilla Firefox 139 became EOL in 2025. |
| 138 | May 27, 2025 |
EOL
Mozilla Firefox 138 became EOL in 2025. |
| 137 | April 29, 2025 |
EOL
Mozilla Firefox 137 became EOL in 2025. |
| 136 | April 1, 2025 |
EOL
Mozilla Firefox 136 became EOL in 2025. |
By the Year
In 2026 there have been 420 vulnerabilities in Mozilla Firefox with an average score of 7.8 out of ten. Last year, in 2025 Firefox had 189 security vulnerabilities published. That is, 231 more vulnerabilities have already been reported in 2026 as compared to last year. However, the average CVE base score of the vulnerabilities in 2026 is greater by 0.26.
| Year | Vulnerabilities | Average Score |
|---|---|---|
| 2026 | 420 | 7.81 |
| 2025 | 189 | 7.54 |
| 2024 | 190 | 7.15 |
| 2023 | 180 | 7.38 |
| 2022 | 159 | 7.44 |
| 2021 | 123 | 7.13 |
| 2020 | 148 | 7.27 |
| 2019 | 121 | 7.44 |
| 2018 | 312 | 7.82 |
It may take a day or so for new Firefox vulnerabilities to show up in the stats or in the list of recent security vulnerabilities. Additionally vulnerabilities may be tagged under a different product or component name.
Recent Mozilla Firefox Security Vulnerabilities
Firefox 154/153.1 memcorr flaw (CVE-2026-84144)
CVE-2026-84144
7.5 - High
- September 01, 2026
Internally found bugs present in Thunderbird 154 and Thunderbird ESR 153.1. 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 155, Firefox ESR 153.2, Thunderbird 155, and Thunderbird 153.2.
Buffer Overflow
Firefox <155 memory corruption CVE-2026-84143
CVE-2026-84143
9.8 - Critical
- September 01, 2026
Internally found bugs present in Thunderbird 154, Thunderbird ESR 153.1 and Thunderbird ESR 140.14. 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 155, Firefox ESR 140.15, Firefox ESR 153.2, Thunderbird 155, Thunderbird 140.15, and Thunderbird 153.2.
Information Disclosure
Memory Corruption in Firefox 154 (CVE-2026-84142)
CVE-2026-84142
9.8 - Critical
- September 01, 2026
Internally found bugs present in Thunderbird 154. 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 155 and Thunderbird 155.
Information Disclosure
Firefox Integer Overflow in ImageLib (Graphics) Before v155
CVE-2026-84141
9.8 - Critical
- September 01, 2026
Integer overflow in the Graphics: ImageLib component. This vulnerability was fixed in Firefox 155, Firefox ESR 153.2, Thunderbird 155, and Thunderbird 153.2.
Integer Overflow or Wraparound
Firefox 153.x+ Site Isolation DOM Navigation Vulnerability (CVE-2026-84140)
CVE-2026-84140
9.8 - Critical
- September 01, 2026
Site isolation issue in the DOM: Navigation component. This vulnerability was fixed in Firefox 155, Firefox ESR 153.2, Thunderbird 155, and Thunderbird 153.2.
Origin Validation Error
Firefox DOM Events clickjacking before v155
CVE-2026-84139
9.8 - Critical
- September 01, 2026
Clickjacking issue in the DOM: Events component. This vulnerability was fixed in Firefox 155, Firefox ESR 153.2, Thunderbird 155, and Thunderbird 153.2.
Clickjacking
DoS in Firefox PDF Viewer (CVE-2026-84138)
CVE-2026-84138
7.5 - High
- September 01, 2026
Denial-of-service in the PDF Viewer component. This vulnerability was fixed in Firefox 155 and Thunderbird 155.
Resource Exhaustion
Firefox DOM Spoofing in Core & HTML Fixed in 155
CVE-2026-84137
9.8 - Critical
- September 01, 2026
Spoofing issue in the DOM: Core & HTML component. This vulnerability was fixed in Firefox 155, Firefox ESR 153.2, Thunderbird 155, and Thunderbird 153.2.
User Interface (UI) Misrepresentation of Critical Information
Firefox DOM Navigation Component Vulnerability (Fixed in 155)
CVE-2026-84136
9.8 - Critical
- September 01, 2026
Other issue in the DOM: Navigation component. This vulnerability was fixed in Firefox 155, Firefox ESR 153.2, Thunderbird 155, and Thunderbird 153.2.
Information Disclosure
Mozilla Firefox Focus Android CVE-2026-84135: Other Issue
CVE-2026-84135
9.8 - Critical
- September 01, 2026
Other issue in Firefox Focus for Android. This vulnerability was fixed in Firefox 155.
Information Disclosure
Firefox 155+ Profile Backup component flaw (CVE-2026-84134)
CVE-2026-84134
9.8 - Critical
- September 01, 2026
Other issue in the Profile Backup component. This vulnerability was fixed in Firefox 155, Firefox ESR 153.2, Thunderbird 155, and Thunderbird 153.2.
Information Disclosure
Firefox DOM Push Subscriptions site isolation flaw before v155
CVE-2026-84133
9.8 - Critical
- September 01, 2026
Site isolation issue in the DOM: Push Subscriptions component. This vulnerability was fixed in Firefox 155, Firefox ESR 153.2, Thunderbird 155, and Thunderbird 153.2.
Origin Validation Error
Firefox <155 Info Disclosure in Networking HTTP Component
CVE-2026-84132
7.5 - High
- September 01, 2026
Information disclosure in the Networking: HTTP component. This vulnerability was fixed in Firefox 155, Firefox ESR 153.2, Thunderbird 155, and Thunderbird 153.2.
Information Disclosure
Firefox WebGPU Info Disclosure (before v155)
CVE-2026-84130
7.5 - High
- September 01, 2026
Information disclosure in the Graphics: WebGPU component. This vulnerability was fixed in Firefox 155, Firefox ESR 153.2, Thunderbird 155, and Thunderbird 153.2.
Information Disclosure
Firefox SiteIsolation DOM Navigation Bug Fixed V155 ESR153.2
CVE-2026-84129
9.8 - Critical
- September 01, 2026
Site isolation issue in the DOM: Navigation component. This vulnerability was fixed in Firefox 155, Firefox ESR 153.2, Thunderbird 155, and Thunderbird 153.2.
Origin Validation Error
Firefox Privilege Escalation via WebDriver BiDi
CVE-2026-84128
8.8 - High
- September 01, 2026
Privilege escalation in the WebDriver BiDi component. This vulnerability was fixed in Firefox 155 and Thunderbird 155.
Authorization
Firefox Android WebExtensions Info Disclosure
CVE-2026-84127
4.3 - Medium
- September 01, 2026
Information disclosure in the WebExtensions component in Firefox for Android. This vulnerability was fixed in Firefox 155.
Information Disclosure
Firefox Grid Layout Boundary Condition Vulnerability (CVE-2026-84126)
CVE-2026-84126
4.3 - Medium
- September 01, 2026
Incorrect boundary conditions in the Layout: Grid component. This vulnerability was fixed in Firefox 155 and Thunderbird 155.
Classic Buffer Overflow
Use-After-Free in Firefox Core & HTML DOM Component <155
CVE-2026-84125
5.4 - Medium
- September 01, 2026
Use-after-free in the DOM: Core & HTML component. This vulnerability was fixed in Firefox 155, Firefox ESR 153.2, Thunderbird 155, and Thunderbird 153.2.
Dangling pointer
Use-after-free in Firefox DOM: Core & HTML (before 155)
CVE-2026-84124
5.4 - Medium
- September 01, 2026
Use-after-free in the DOM: Core & HTML component. This vulnerability was fixed in Firefox 155, Firefox ESR 140.15, Firefox ESR 153.2, Thunderbird 155, Thunderbird 140.15, and Thunderbird 153.2.
Dangling pointer
Firefox Privilege Escalation via WebGPU Use-After-Free (before 155)
CVE-2026-84123
8.8 - High
- September 01, 2026
Privilege escalation due to use-after-free in the Graphics: WebGPU component. This vulnerability was fixed in Firefox 155, Firefox ESR 153.2, Thunderbird 155, and Thunderbird 153.2.
Dangling pointer
UAF in Firefox Media Component (fixed 155/ESR 140.15/153.2)
CVE-2026-84122
5.4 - Medium
- September 01, 2026
Use-after-free in the Audio/Video component. This vulnerability was fixed in Firefox 155, Firefox ESR 140.15, Firefox ESR 153.2, Thunderbird 155, Thunderbird 140.15, and Thunderbird 153.2.
Dangling pointer
Use-after-Free in Firefox 155 JS GC component (before 155)
CVE-2026-84118
5.4 - Medium
- September 01, 2026
Use-after-free in the JavaScript: GC component. This vulnerability was fixed in Firefox 155, Firefox ESR 153.2, Thunderbird 155, and Thunderbird 153.2.
Dangling pointer
Privilege Escalation in Firefox Android 155+
CVE-2026-84117
8.8 - High
- September 01, 2026
Privilege escalation in Firefox for Android. This vulnerability was fixed in Firefox 155.
Authorization
Firefox 154 ESR 115.39 Memory Corruption Vulnerability
CVE-2026-84145
7.5 - High
- September 01, 2026
Internally found bugs present in Thunderbird 154, Thunderbird ESR 153.1 and Thunderbird ESR 140.14. 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 155, Firefox ESR 115.40, Firefox ESR 140.15, Firefox ESR 153.2, Thunderbird 155, Thunderbird 140.15, and Thunderbird 153.2.
Buffer Overflow
Firefox Priv Esc Prt Err in Graphics Comp (<155, ESR<115.40, ESR<140.15, ESR<153.2)
CVE-2026-84131
8.8 - High
- September 01, 2026
Privilege escalation due to invalid pointer in the Graphics component. This vulnerability was fixed in Firefox 155, Firefox ESR 115.40, Firefox ESR 140.15, Firefox ESR 153.2, Thunderbird 155, Thunderbird 140.15, and Thunderbird 153.2.
Release of Invalid Pointer or Reference
Firefox Sandbox escape via DOM UAF (fixed in 155)
CVE-2026-84121
9.6 - Critical
- September 01, 2026
Sandbox escape due to use-after-free in the DOM: Security component. This vulnerability was fixed in Firefox 155, Firefox ESR 115.40, Firefox ESR 140.15, Firefox ESR 153.2, Thunderbird 155, Thunderbird 140.15, and Thunderbird 153.2.
Dangling pointer
Use-after-free in Audio/Video component of Firefox <155 (ESR 115.40)
CVE-2026-84120
5.4 - Medium
- September 01, 2026
Use-after-free in the Audio/Video component. This vulnerability was fixed in Firefox 155, Firefox ESR 115.40, Firefox ESR 140.15, Firefox ESR 153.2, Thunderbird 155, Thunderbird 140.15, and Thunderbird 153.2.
Dangling pointer
Firefox Sandbox Escape UAF in DOM Navigation Component
CVE-2026-84119
9.6 - Critical
- September 01, 2026
Sandbox escape due to use-after-free in the DOM: Navigation component. This vulnerability was fixed in Firefox 155, Firefox ESR 115.40, Firefox ESR 140.15, Firefox ESR 153.2, Thunderbird 155, Thunderbird 140.15, and Thunderbird 153.2.
Dangling pointer
Firefox iOS 155.0: Cross-Origin Popup Navigation Stall
CVE-2026-81267
5.4 - Medium
- August 31, 2026
A malicious webpage could stall a popup's cross-origin navigation after commit, causing the address bar to display the destination origin while continuing to render attacker-controlled content. This vulnerability was fixed in Firefox for iOS 155.0.
User Interface (UI) Misrepresentation of Critical Information
Memory corruption bugs in Firefox 153
CVE-2026-74989
9.8 - Critical
- August 18, 2026
Internally found bugs present in Thunderbird 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.
Buffer Overflow
Firefox ESR 153.0 Memory Corruption Vulnerability (fixed in 153.1)
CVE-2026-74988
9.8 - Critical
- August 18, 2026
Internally found bugs present in Thunderbird ESR 153.0 and Thunderbird 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.
Buffer Overflow
DoS in Firefox Widget component before 154/ESR153.1
CVE-2026-74982
7.5 - High
- August 18, 2026
Denial-of-service in the Widget component. This vulnerability was fixed in Firefox 154, Firefox ESR 153.1, Thunderbird 154, and Thunderbird 153.1.
Resource Exhaustion
Race Condition in JS Engine, Firefox <154, fixed v154
CVE-2026-74984
6.8 - Medium
- August 18, 2026
Race condition in the JavaScript Engine component. This vulnerability was fixed in Firefox 154, Firefox ESR 153.1, Thunderbird 154, and Thunderbird 153.1.
Race Condition
Firefox 154 ESR 153.1 Fixed PrivEsc in Enterprise Policies
CVE-2026-74985
9.8 - Critical
- August 18, 2026
Privilege escalation in the Enterprise Policies component. This vulnerability was fixed in Firefox 154, Firefox ESR 153.1, Thunderbird 154, and Thunderbird 153.1.
Improper Privilege Management
CSS Parsing Component Site Isolation Flaw Fixed in Firefox 154 & ESR 153.1
CVE-2026-74986
9.1 - Critical
- August 18, 2026
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.
Information Disclosure
Site Isolation Vulnerability in Web Codecs (Firefox <154, Thunderbird <154)
CVE-2026-74981
8.1 - High
- August 18, 2026
Site isolation issue in the Audio/Video: Web Codecs component. This vulnerability was fixed in Firefox 154, Firefox ESR 153.1, Thunderbird 154, and Thunderbird 153.1.
Origin Validation Error
Clickjacking Vulnerability in Firefox Android Downloads Component
CVE-2026-74980
6.5 - Medium
- August 18, 2026
Clickjacking issue in the Downloads component in Firefox for Android. This vulnerability was fixed in Firefox 154.
Clickjacking
Mitigation bypass in Addons Manager (Firefox 154, ESR 153.1, Thunderbird 154)
CVE-2026-74979
9.8 - Critical
- August 18, 2026
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.
Authorization
Clickjacking in Firefox/Thunderbird widget component before v154
CVE-2026-74978
8.1 - High
- August 18, 2026
Clickjacking issue in the Widget component. This vulnerability was fixed in Firefox 154, Firefox ESR 153.1, Thunderbird 154, and Thunderbird 153.1.
Clickjacking
Site Isolation Flaw in WebRender of Firefox/Thunderbird (v<154)
CVE-2026-74968
5.4 - Medium
- August 18, 2026
Site isolation issue in the Graphics: WebRender component. This vulnerability was fixed in Firefox 154, Firefox ESR 153.1, Thunderbird 154, and Thunderbird 153.1.
Origin Validation Error
Site isolation flaw in Firefox Graphics before v154
CVE-2026-74970
5.4 - Medium
- August 18, 2026
Site isolation issue in the Graphics component. This vulnerability was fixed in Firefox 154, Firefox ESR 153.1, Thunderbird 154, and Thunderbird 153.1.
Origin Validation Error
Firefox & Thunderbird Graphics INT Overflow CVE-2026-74977 Fixed 154
CVE-2026-74977
7.5 - High
- August 18, 2026
Integer overflow in the Graphics component. This vulnerability was fixed in Firefox 154, Firefox ESR 153.1, Thunderbird 154, and Thunderbird 153.1.
Integer Overflow or Wraparound
Firefox Android Downloads Spoofing Vulnerability
CVE-2026-74975
5.4 - Medium
- August 18, 2026
Spoofing issue in the Downloads component in Firefox for Android. This vulnerability was fixed in Firefox 154.
User Interface (UI) Misrepresentation of Critical Information
Firefox 154: Information Disclosure in Form Autofill
CVE-2026-74966
7.5 - High
- August 18, 2026
Information disclosure in the Form Autofill component. This vulnerability was fixed in Firefox 154, Firefox ESR 153.1, Thunderbird 154, and Thunderbird 153.1.
Privacy violation
Web Audio side-channel in Firefox 154, Thunderbird 154
CVE-2026-74961
9.1 - Critical
- August 18, 2026
Side-channel in the Web Audio component. This vulnerability was fixed in Firefox 154, Firefox ESR 153.1, Thunderbird 154, and Thunderbird 153.1.
Side Channel Attack
CVE-2026-74958: WebRTC Info Disclosure before Firefox+Thunderbird 154
CVE-2026-74958
7.5 - High
- August 18, 2026
Information disclosure in the WebRTC component. This vulnerability was fixed in Firefox 154, Firefox ESR 153.1, Thunderbird 154, and Thunderbird 153.1.
Clickjacking
Same-Origin Policy Bypass in Service Workers (Firefox <154, Thunderbird <154)
CVE-2026-74956
9.1 - Critical
- August 18, 2026
Same-origin policy bypass in the DOM: Service Workers component. This vulnerability was fixed in Firefox 154, Firefox ESR 153.1, Thunderbird 154, and Thunderbird 153.1.
Object Type Confusion
Mozilla Firefox AppUpd PrivEsc via Application Update Vulnerability
CVE-2026-74952
8.8 - High
- August 18, 2026
Privilege escalation in the Application Update component. This vulnerability was fixed in Firefox 154, Thunderbird 154, Firefox ESR 153.2, and Thunderbird 153.2.
Improper Privilege Management
Privilege Escalation via Request Handling in Firefox 154 & Thunderbird 154
CVE-2026-74955
8.8 - High
- August 18, 2026
Privilege escalation in the Request Handling component. This vulnerability was fixed in Firefox 154, Firefox ESR 153.1, Thunderbird 154, and Thunderbird 153.1.
Improper Privilege Management
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