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Recent Mozilla Thunderbird Security Advisories
| Advisory | Title | Published |
|---|---|---|
| mfsa2026-43 | Security Vulnerabilities fixed in Thunderbird 150.0.2 mfsa2026-43 | May 8, 2026 |
| mfsa2026-44 | Security Vulnerabilities fixed in Thunderbird 140.10.2 mfsa2026-44 | May 8, 2026 |
| mfsa2026-38 | Security Vulnerabilities fixed in Thunderbird 150.0.1 mfsa2026-38 | April 30, 2026 |
| mfsa2026-39 | Security Vulnerabilities fixed in Thunderbird 140.10.1 mfsa2026-39 | April 30, 2026 |
| mfsa2026-34 | Security Vulnerabilities fixed in Thunderbird 140.10 mfsa2026-34 | April 21, 2026 |
| mfsa2026-33 | Security Vulnerabilities fixed in Thunderbird 150 mfsa2026-33 | April 21, 2026 |
| mfsa2026-28 | Security Vulnerabilities fixed in Thunderbird 149.0.2 mfsa2026-28 | April 7, 2026 |
| mfsa2026-29 | Security Vulnerabilities fixed in Thunderbird 140.9.1 mfsa2026-29 | April 7, 2026 |
| mfsa2026-24 | Security Vulnerabilities fixed in Thunderbird 140.9 mfsa2026-24 | March 24, 2026 |
| mfsa2026-23 | Security Vulnerabilities fixed in Thunderbird 149 mfsa2026-23 | March 24, 2026 |
By the Year
In 2026 there have been 170 vulnerabilities in Mozilla Thunderbird with an average score of 8.3 out of ten. Last year, in 2025 Thunderbird had 157 security vulnerabilities published. That is, 13 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 0.62.
| Year | Vulnerabilities | Average Score |
|---|---|---|
| 2026 | 170 | 8.28 |
| 2025 | 157 | 7.65 |
| 2024 | 119 | 7.19 |
| 2023 | 102 | 7.49 |
| 2022 | 116 | 7.56 |
| 2021 | 73 | 7.23 |
| 2020 | 80 | 7.59 |
| 2019 | 62 | 8.21 |
| 2018 | 167 | 8.24 |
It may take a day or so for new Thunderbird 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 Thunderbird Security Vulnerabilities
Firefox ESR 140.10.2 WebRTC Vulnerability
CVE-2026-8094
9.8 - Critical
- May 07, 2026
Other issue in the WebRTC component. This vulnerability was fixed in Firefox ESR 140.10.2 and Thunderbird 140.10.2.
Code Injection
Firefox 150.0.1 Memcor bugs may allow arbitrary code execution
CVE-2026-8093
8.1 - High
- May 07, 2026
Memory safety bugs present in Thunderbird 150.0.1. 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 150.0.2 and Thunderbird 150.0.2.
Buffer Overflow
Firefox 115.35.1/140.10.1/150.0.1 Memory Safety Bug
CVE-2026-8092
8.1 - High
- May 07, 2026
Memory safety bugs present in Thunderbird ESR 140.10.1 and Thunderbird 150.0.1. 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 150.0.2, Firefox ESR 140.10.2, Firefox ESR 115.35.2, Thunderbird 150.0.2, and Thunderbird 140.10.2.
Out-of-bounds Read
Firefox ESR AV Playback boundary flaw before 140.10.2
CVE-2026-8091
9.8 - Critical
- May 07, 2026
Incorrect boundary conditions in the Audio/Video: Playback component. This vulnerability was fixed in Firefox 150, Thunderbird 150, Firefox ESR 140.10.1, Thunderbird 140.10.1, and Firefox ESR 115.35.2.
Improper Check for Unusual or Exceptional Conditions
Use-after-free in Firefox DOM Networking pre-150.0.2
CVE-2026-8090
7.3 - High
- May 07, 2026
Use-after-free in the DOM: Networking component. This vulnerability was fixed in Firefox 150.0.2, Firefox ESR 140.10.2, Firefox ESR 115.35.2, Thunderbird 150.0.2, and Thunderbird 140.10.2.
Dangling pointer
Firefox Sandbox Escape in WebRTC Networking before ESR 140.10.1
CVE-2026-7321
9.6 - Critical
- April 28, 2026
Sandbox escape due to incorrect boundary conditions in the WebRTC: Networking component. This vulnerability was fixed in Firefox 150, Thunderbird 150, Firefox ESR 140.10.1, and Thunderbird 140.10.1.
Classic Buffer Overflow
Memory safety bugs in Firefox 150.0.0 (fixed 150.0.1)
CVE-2026-7324
7.3 - High
- April 28, 2026
Memory safety bugs present in Thunderbird 150.0.0. 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 150.0.1 and Thunderbird 150.0.1.
Buffer Overflow
Memory Safety Bug in Firefox ESR 140.10.0 & Thunderbird 140.10.0
CVE-2026-7323
7.3 - High
- April 28, 2026
Memory safety bugs present in Thunderbird ESR 140.10.0 and Thunderbird 150.0.0. 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 150.0.1, Firefox ESR 140.10.1, Thunderbird 150.0.1, and Thunderbird 140.10.1.
Buffer Overflow
Memory safety bugs in Firefox ESR 115.35.0/140.10.0 & 150.0.0 (fixed 150.0.1)
CVE-2026-7322
7.3 - High
- April 28, 2026
Memory safety bugs present in Thunderbird ESR 140.10.0 and Thunderbird 150.0.0. 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 150.0.1, Firefox ESR 140.10.1, Firefox ESR 115.35.1, Thunderbird 150.0.1, and Thunderbird 140.10.1.
Buffer Overflow
Firefox Audio/Video Boundary Bug Info Disclosure (fixed in 150.0.1)
CVE-2026-7320
7.5 - High
- April 28, 2026
Information disclosure due to incorrect boundary conditions in the Audio/Video component. This vulnerability was fixed in Firefox 150.0.1, Firefox ESR 140.10.1, Firefox ESR 115.35.1, Thunderbird 150.0.1, and Thunderbird 140.10.1.
Buffer Overflow
Firefox 149 / ESR 140.9 Memory Safety Bugs (Arbitrary Code Exec)
CVE-2026-6786
8.1 - High
- April 21, 2026
Memory safety bugs present in Firefox ESR 140.9, Thunderbird ESR 140.9, Firefox 149 and Thunderbird 149. 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 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.
Dangling pointer
Mozilla Firefox Memory Safety Bug (ESR 115.34, 115.35, ESR 140.9/140.10, 149)
CVE-2026-6785
8.1 - High
- April 21, 2026
Memory safety bugs present in Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird ESR 140.9, Firefox 149 and Thunderbird 149. 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 150, Firefox ESR 115.35, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.
Out-of-bounds Read
Memory Safety Bugs in Firefox 149 & Thunderbird 149
CVE-2026-6784
7.5 - High
- April 21, 2026
Memory safety bugs present in Firefox 149 and Thunderbird 149. 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 150 and Thunderbird 150.
Out-of-bounds Read
Firefox 150 AV Playback CVE20266783 Integer Overflow
CVE-2026-6783
5.3 - Medium
- April 21, 2026
Incorrect boundary conditions, integer overflow in the Audio/Video: Playback component. This vulnerability was fixed in Firefox 150 and Thunderbird 150.
Integer Overflow or Wraparound
Info Disclosure via Firefox IP Protection Component
CVE-2026-6782
7.5 - High
- April 21, 2026
Information disclosure in the IP Protection component. This vulnerability was fixed in Firefox 150 and Thunderbird 150.
Information Disclosure
DoS in Firefox AV Playback Component (CVE-2026-6781)
CVE-2026-6781
7.5 - High
- April 21, 2026
Denial-of-service in the Audio/Video: Playback component. This vulnerability was fixed in Firefox 150 and Thunderbird 150.
Resource Exhaustion
Firefox A/V Playback DoS Vulnerability
CVE-2026-6780
7.5 - High
- April 21, 2026
Denial-of-service in the Audio/Video: Playback component. This vulnerability was fixed in Firefox 150 and Thunderbird 150.
Resource Exhaustion
Mozilla Firefox JS Engine CVE-2026-6779 (Other issue)
CVE-2026-6779
5.3 - Medium
- April 21, 2026
Other issue in the JavaScript Engine component. This vulnerability was fixed in Firefox 150 and Thunderbird 150.
Buffer Overflow
Firefox 150 - Invalid Pointer in Audio/Video Playback
CVE-2026-6778
5.3 - Medium
- April 21, 2026
Invalid pointer in the Audio/Video: Playback component. This vulnerability was fixed in Firefox 150 and Thunderbird 150.
Access of Uninitialized Pointer
CVE-2026-6777: Firefox DNS Component Vulnerability
CVE-2026-6777
5.3 - Medium
- April 21, 2026
Other issue in the Networking: DNS component. This vulnerability was fixed in Firefox 150 and Thunderbird 150.
Improper Input Validation
Firefox <150 WebRTC Networking boundary condition flaw (CVE-2026-6776)
CVE-2026-6776
7.8 - High
- April 21, 2026
Incorrect boundary conditions in the WebRTC: Networking component. This vulnerability was fixed in Firefox 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.
Buffer Overflow
Firefox WebRTC Improper Boundary Check (CVE-2026-6775)
CVE-2026-6775
5.3 - Medium
- April 21, 2026
Incorrect boundary conditions in the WebRTC component. This vulnerability was fixed in Firefox 150 and Thunderbird 150.
Buffer Overflow
DOM Mitigation Bypass in Firefox Security Component
CVE-2026-6774
5.4 - Medium
- April 21, 2026
Mitigation bypass in the DOM: Security component. This vulnerability was fixed in Firefox 150 and Thunderbird 150.
Protection Mechanism Failure
Firefox NSS Libraries Boundary Cond. before 150
CVE-2026-6772
7.5 - High
- April 21, 2026
Incorrect boundary conditions in the Libraries component in NSS. This vulnerability was fixed in Firefox 150, Firefox ESR 115.35, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.
Improper Check for Unusual or Exceptional Conditions
Firefox WebGPU Integer Overflow DoS
CVE-2026-6773
7.5 - High
- April 21, 2026
Denial-of-service due to integer overflow in the Graphics: WebGPU component. This vulnerability was fixed in Firefox 150 and Thunderbird 150.
Integer Overflow or Wraparound
Firefox 150 DOM Mitigation Bypass in Security Component
CVE-2026-6771
9.8 - Critical
- April 21, 2026
Mitigation bypass in the DOM: Security component. This vulnerability was fixed in Firefox 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.
Authentication Bypass Using an Alternate Path or Channel
IndexedDB flaw in Firefox <=150 (ESR 140.10)
CVE-2026-6770
6.5 - Medium
- April 21, 2026
Other issue in the Storage: IndexedDB component. This vulnerability was fixed in Firefox 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.
Information Disclosure
Priv Escalation in Firefox Debugger (before 150)
CVE-2026-6769
8.8 - High
- April 21, 2026
Privilege escalation in the Debugger component. This vulnerability was fixed in Firefox 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.
Improper Privilege Management
CVE-2026-6768: Mitigation Bypass in Firefox Cookies Handling
CVE-2026-6768
9.8 - Critical
- April 21, 2026
Mitigation bypass in the Networking: Cookies component. This vulnerability was fixed in Firefox 150 and Thunderbird 150.
Authentication Bypass Using an Alternate Path or Channel
NSS Lib Other Issue (Fixed in Firefox 150/ESR 115.35)
CVE-2026-6767
5.3 - Medium
- April 21, 2026
Other issue in the Libraries component in NSS. This vulnerability was fixed in Firefox 150, Firefox ESR 115.35, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.
Buffer Overflow
Firefox NSS boundary overflow (before 150/140.10)
CVE-2026-6766
7.5 - High
- April 21, 2026
Incorrect boundary conditions in the Libraries component in NSS. This vulnerability was fixed in Firefox 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.
Improper Check for Unusual or Exceptional Conditions
Firefox Autofill Info Disclosure before 150
CVE-2026-6765
5.3 - Medium
- April 21, 2026
Information disclosure in the Form Autofill component. This vulnerability was fixed in Firefox 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.
Privacy violation
Firefox DOM Boundary Condition Flaw in Device Interfaces (fixed in v150)
CVE-2026-6764
6.5 - Medium
- April 21, 2026
Incorrect boundary conditions in the DOM: Device Interfaces component. This vulnerability was fixed in Firefox 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.
Buffer Overflow
Firefox File Handling Mitigation Bypass (Before 150/ESR 140.10)
CVE-2026-6763
6.5 - Medium
- April 21, 2026
Mitigation bypass in the File Handling component. This vulnerability was fixed in Firefox 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.
Protection Mechanism Failure
Firefox DOM Spoofing Vulnerability (pre-150) Core & HTML
CVE-2026-6762
6.3 - Medium
- April 21, 2026
Spoofing issue in the DOM: Core & HTML component. This vulnerability was fixed in Firefox 150, Firefox ESR 115.35, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.
Authentication Bypass by Spoofing
Firefox 150 PrivEsc via Networking Component
CVE-2026-6761
8.8 - High
- April 21, 2026
Privilege escalation in the Networking component. This vulnerability was fixed in Firefox 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.
Improper Privilege Management
Firefox Networking Cookies Mitigation Bypass CVE-2026-6760
CVE-2026-6760
9.8 - Critical
- April 21, 2026
Mitigation bypass in the Networking: Cookies component. This vulnerability was fixed in Firefox 150 and Thunderbird 150.
Authentication Bypass Using an Alternate Path or Channel
Use-after-free in Firefox Widget Cocoa (150)
CVE-2026-6759
7.5 - High
- April 21, 2026
Use-after-free in the Widget: Cocoa component. This vulnerability was fixed in Firefox 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.
Dangling pointer
Use-after-free: WebAssembly Component in Firefox
CVE-2026-6758
7.5 - High
- April 21, 2026
Use-after-free in the JavaScript: WebAssembly component. This vulnerability was fixed in Firefox 150 and Thunderbird 150.
Dangling pointer
Firefox WebAsm Null Pointer Bug Before v150 (CVE-2026-6757)
CVE-2026-6757
6.3 - Medium
- April 21, 2026
Invalid pointer in the JavaScript: WebAssembly component. This vulnerability was fixed in Firefox 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.
Access of Uninitialized Pointer
Mozilla Firefox postMessage DOM Mitigation Bypass (CVE20266755)
CVE-2026-6755
6.5 - Medium
- April 21, 2026
Mitigation bypass in the DOM: postMessage component. This vulnerability was fixed in Firefox 150 and Thunderbird 150.
Session Riding
UAF in JavaScript Engine, fixed in Firefox 150/ESR 115.35/140.10
CVE-2026-6754
7.5 - High
- April 21, 2026
Use-after-free in the JavaScript Engine component. This vulnerability was fixed in Firefox 150, Firefox ESR 115.35, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.
Dangling pointer
Firefox WebRTC Boundary Condition Vulnerability (fixed in 150/ESR 140.10)
CVE-2026-6753
7.3 - High
- April 21, 2026
Incorrect boundary conditions in the WebRTC component. This vulnerability was fixed in Firefox 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.
Buffer Overflow
Firefox WebRTC Boundary Condition Flaw (before v150 / ESR 115.35)
CVE-2026-6752
7.3 - High
- April 21, 2026
Incorrect boundary conditions in the WebRTC component. This vulnerability was fixed in Firefox 150, Firefox ESR 115.35, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.
Buffer Overflow
Pre-150 Firefox Web Codecs Uninitialized Memory Vulnerability
CVE-2026-6751
7.3 - High
- April 21, 2026
Uninitialized memory in the Audio/Video: Web Codecs component. This vulnerability was fixed in Firefox 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.
Use of Uninitialized Variable
Firefox PrivEsc via Graphics:WebRender before 150
CVE-2026-6750
8.8 - High
- April 21, 2026
Privilege escalation in the Graphics: WebRender component. This vulnerability was fixed in Firefox 150, Firefox ESR 115.35, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.
Improper Privilege Management
Firefox Canvas2D Info Disclosure via Uninit Mem, Fixed 150/ESR115.35
CVE-2026-6749
7.5 - High
- April 21, 2026
Information disclosure due to uninitialized memory in the Graphics: Canvas2D component. This vulnerability was fixed in Firefox 150, Firefox ESR 115.35, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.
Use of Uninitialized Resource
Web Codecs Uninitialized Mem in Firefox <150 (Fixed 150)
CVE-2026-6748
9.8 - Critical
- April 21, 2026
Uninitialized memory in the Audio/Video: Web Codecs component. This vulnerability was fixed in Firefox 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.
Use of Uninitialized Variable
Firefox <150 WebRTC Use-after-free Vulnerability
CVE-2026-6747
7.5 - High
- April 21, 2026
Use-after-free in the WebRTC component. This vulnerability was fixed in Firefox 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.
Dangling pointer
Use-after-free in Firefox Core&HTML before v150
CVE-2026-6746
7.5 - High
- April 21, 2026
Use-after-free in the DOM: Core & HTML component. This vulnerability was fixed in Firefox 150, Firefox ESR 115.35, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.
Dangling pointer
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