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Recent Mozilla Thunderbird Security Advisories
| Advisory | Title | Published |
|---|---|---|
| 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 |
| mfsa2026-16 | Security Vulnerabilities fixed in Thunderbird 148 mfsa2026-16 | February 24, 2026 |
| mfsa2026-17 | Security Vulnerabilities fixed in Thunderbird 140.8 mfsa2026-17 | February 24, 2026 |
| mfsa2026-11 | Security Vulnerabilities fixed in Thunderbird 147.0.2 and 140.7.2 mfsa2026-11 | February 16, 2026 |
| mfsa2026-08 | Security Vulnerabilities fixed in Thunderbird 140.7.1 mfsa2026-08 | January 27, 2026 |
| mfsa2026-07 | Security Vulnerabilities fixed in Thunderbird 147.0.1 mfsa2026-07 | January 27, 2026 |
| mfsa2026-04 | Security Vulnerabilities fixed in Thunderbird 147 mfsa2026-04 | January 13, 2026 |
| mfsa2026-05 | Security Vulnerabilities fixed in Thunderbird 140.7 mfsa2026-05 | January 13, 2026 |
| mfsa2025-95 | Security Vulnerabilities fixed in Thunderbird 146 mfsa2025-95 | December 9, 2025 |
By the Year
In 2026 there have been 109 vulnerabilities in Mozilla Thunderbird with an average score of 8.7 out of ten. Last year, in 2025 Thunderbird had 157 security vulnerabilities published. If vulnerabilities keep coming in at the current rate, it appears that number of security vulnerabilities in Thunderbird in 2026 could surpass last years number. However, the average CVE base score of the vulnerabilities in 2026 is greater by 1.02.
| Year | Vulnerabilities | Average Score |
|---|---|---|
| 2026 | 109 | 8.69 |
| 2025 | 157 | 7.66 |
| 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
Thunderbird <149 Vulnerable Parser Reads OOB via Malformed Mail (CVE-2026-4371)
CVE-2026-4371
7.4 - High
- March 24, 2026
A malicious mail server could send malformed strings with negative lengths, causing the parser to read memory outside the buffer. If a mail server or connection to a mail server were compromised, an attacker could cause the parser to malfunction, potentially crashing Thunderbird or leaking sensitive data. This vulnerability affects Thunderbird < 149 and Thunderbird < 140.9.
Buffer Over-read
Thunderbird Email Client Spoofing Issue <149, <140.9
CVE-2026-3889
6.5 - Medium
- March 24, 2026
Spoofing issue in Thunderbird. This vulnerability affects Thunderbird < 149 and Thunderbird < 140.9.
User Interface (UI) Misrepresentation of Critical Information
Memory safety bugs in Firefox <149 (CVE-2026-4729)
CVE-2026-4729
9.8 - Critical
- March 24, 2026
Memory safety bugs present in Firefox 148 and Thunderbird 148. 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 affects Firefox < 149 and Thunderbird < 149.
Classic Buffer Overflow
Memory Safety Bug in Firefox (ESR 115.33/140.8 & 148) prior to v149
CVE-2026-4721
9.8 - Critical
- March 24, 2026
Memory safety bugs present in Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird ESR 140.8, Firefox 148 and Thunderbird 148. 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 affects Firefox < 149, Firefox ESR < 115.34, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
Classic Buffer Overflow
Mozilla Firefox <149 & ESR <140.9 Memory Corruption (Thunderbird)
CVE-2026-4720
9.8 - Critical
- March 24, 2026
Memory safety bugs present in Firefox ESR 140.8, Thunderbird ESR 140.8, Firefox 148 and Thunderbird 148. 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 affects Firefox < 149, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
Classic Buffer Overflow
Firefox Graphics:Text Boundary Condition Flaw (pre-149 / ESR<140.9)
CVE-2026-4719
7.5 - High
- March 24, 2026
Incorrect boundary conditions in the Graphics: Text component. This vulnerability affects Firefox < 149, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
Buffer Overflow
Firefox Privacy Anti-Tracking Spoofing Vulnerability
CVE-2026-4728
6.5 - Medium
- March 24, 2026
Spoofing issue in the Privacy: Anti-Tracking component. This vulnerability affects Firefox < 149 and Thunderbird < 149.
Authentication Bypass by Spoofing
Undefined Behavior in WebRTC Signaling of Firefox <149
CVE-2026-4718
8.1 - High
- March 24, 2026
Undefined behavior in the WebRTC: Signaling component. This vulnerability affects Firefox < 149, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
Reliance on Undefined, Unspecified, or Implementation-Defined Behavior
Firefox <149 NSS Libraries DoS (Mozilla)
CVE-2026-4727
7.5 - High
- March 24, 2026
Denial-of-service in the Libraries component in NSS. This vulnerability affects Firefox < 149 and Thunderbird < 149.
Resource Exhaustion
Denial-of-Service in Firefox XML Component (CVE-2026-4726)
CVE-2026-4726
7.5 - High
- March 24, 2026
Denial-of-service in the XML component. This vulnerability affects Firefox < 149 and Thunderbird < 149.
Resource Exhaustion
Privilege Escalation in Netmonitor of Firefox <149/ESR 140.9
CVE-2026-4717
9.8 - Critical
- March 24, 2026
Privilege escalation in the Netmonitor component. This vulnerability affects Firefox < 149, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
Firefox <149/ESR <140.9: JS Engine uninitialized memory
CVE-2026-4716
9.1 - Critical
- March 24, 2026
Incorrect boundary conditions, uninitialized memory in the JavaScript Engine component. This vulnerability affects Firefox < 149, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
Use of Uninitialized Resource
Uninitialized Memory in Firefox Canvas2D component <149/ESR<140.9
CVE-2026-4715
9.1 - Critical
- March 24, 2026
Uninitialized memory in the Graphics: Canvas2D component. This vulnerability affects Firefox < 149, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
Use of Uninitialized Resource
Firefox Audio/Video Boundary Condition Flaw (v <149, ESR <140.9)
CVE-2026-4714
7.5 - High
- March 24, 2026
Incorrect boundary conditions in the Audio/Video component. This vulnerability affects Firefox < 149, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
Improper Check for Unusual or Exceptional Conditions
FF <149 Graphics Boundary Condition Flaw
CVE-2026-4713
7.5 - High
- March 24, 2026
Incorrect boundary conditions in the Graphics component. This vulnerability affects Firefox < 149, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
Improper Check for Unusual or Exceptional Conditions
Firefox Canvas2D Sandbox Escape due to Use-After-Free
CVE-2026-4725
9.3 - Critical
- March 24, 2026
Sandbox escape due to use-after-free in the Graphics: Canvas2D component. This vulnerability affects Firefox < 149 and Thunderbird < 149.
Dangling pointer
Firefox <149 Info Disclosure via Widget Cocoa Comp (CVE-2026-4712)
CVE-2026-4712
7.5 - High
- March 24, 2026
Information disclosure in the Widget: Cocoa component. This vulnerability affects Firefox < 149, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
Information Disclosure
Firefox <149 Use-after-free in Cocoa Widget Component
CVE-2026-4711
9.8 - Critical
- March 24, 2026
Use-after-free in the Widget: Cocoa component. This vulnerability affects Firefox < 149, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
Dangling pointer
Firefox AV Boundary Condition Flaw v<149/ESR<140.9
CVE-2026-4710
9.8 - Critical
- March 24, 2026
Incorrect boundary conditions in the Audio/Video component. This vulnerability affects Firefox < 149, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
Buffer Overflow
Mozilla Firefox <149 Audio/Video: GMP Boundary Condition Vulnerability
CVE-2026-4709
7.5 - High
- March 24, 2026
Incorrect boundary conditions in the Audio/Video: GMP component. This vulnerability affects Firefox < 149, Firefox ESR < 115.34, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
Improper Check for Unusual or Exceptional Conditions
Firefox Graphics Boundary Flaw (149, ESR<140.9)
CVE-2026-4708
7.5 - High
- March 24, 2026
Incorrect boundary conditions in the Graphics component. This vulnerability affects Firefox < 149, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
Improper Check for Unusual or Exceptional Conditions
Firefox <149 Canvas2D Boundary Condition Flaw (CVE20264707)
CVE-2026-4707
7.5 - High
- March 24, 2026
Incorrect boundary conditions in the Graphics: Canvas2D component. This vulnerability affects Firefox < 149, Firefox ESR < 115.34, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
Improper Check for Unusual or Exceptional Conditions
Firefox <149 & ESR <115.34,140.9 Canvas2D Boundary Condition Vulnerability
CVE-2026-4706
7.5 - High
- March 24, 2026
Incorrect boundary conditions in the Graphics: Canvas2D component. This vulnerability affects Firefox < 149, Firefox ESR < 115.34, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
Improper Check for Unusual or Exceptional Conditions
CVE-2026-4705: WebRTC Signaling UB Firefox <149/ESR <140.9
CVE-2026-4705
9.8 - Critical
- March 24, 2026
Undefined behavior in the WebRTC: Signaling component. This vulnerability affects Firefox < 149, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
Reliance on Undefined, Unspecified, or Implementation-Defined Behavior
Undefined Behavior in Firefox Audio/Video Component (CVE-2026-4724)
CVE-2026-4724
9.1 - Critical
- March 24, 2026
Undefined behavior in the Audio/Video component. This vulnerability affects Firefox < 149 and Thunderbird < 149.
Reliance on Undefined, Unspecified, or Implementation-Defined Behavior
Firefox <149 Denial-of-Service via WebRTC Signaling
CVE-2026-4704
7.5 - High
- March 24, 2026
Denial-of-service in the WebRTC: Signaling component. This vulnerability affects Firefox < 149, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
Resource Exhaustion
Use-After-Free in Firefox JS Engine (<v149)
CVE-2026-4723
9.8 - Critical
- March 24, 2026
Use-after-free in the JavaScript Engine component. This vulnerability affects Firefox < 149 and Thunderbird < 149.
Dangling pointer
Mozilla Firefox <149 JIT Miscompilation in JS Engine (CVE-2026-4702)
CVE-2026-4702
9.8 - Critical
- March 24, 2026
JIT miscompilation in the JavaScript Engine component. This vulnerability affects Firefox < 149, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
Object Type Confusion
Privilege Escalation in Firefox IPC Component
CVE-2026-4722
8.8 - High
- March 24, 2026
Privilege escalation in the IPC component. This vulnerability affects Firefox < 149 and Thunderbird < 149.
Use-after-free in Firefox JS Engine before 149 & ESR <140.9
CVE-2026-4701
9.8 - Critical
- March 24, 2026
Use-after-free in the JavaScript Engine component. This vulnerability affects Firefox < 149, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
Dangling pointer
Firefox <149 Mitigation Bypass in Networking:HTTP Component
CVE-2026-4700
9.8 - Critical
- March 24, 2026
Mitigation bypass in the Networking: HTTP component. This vulnerability affects Firefox < 149, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
Authentication Bypass Using an Alternate Path or Channel
Firefox <149 Boundary Error in Layout Text & Fonts
CVE-2026-4699
7.5 - High
- March 24, 2026
Incorrect boundary conditions in the Layout: Text and Fonts component. This vulnerability affects Firefox < 149, Firefox ESR < 115.34, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
Improper Check for Unusual or Exceptional Conditions
Firefox <149 JIT-Miscompilation SpiderMonkey
CVE-2026-4698
9.8 - Critical
- March 24, 2026
JIT miscompilation in the JavaScript Engine: JIT component. This vulnerability affects Firefox < 149, Firefox ESR < 115.34, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
Object Type Confusion
Firefox <149 Audio/Video Web Codecs boundary flaw
CVE-2026-4697
7.5 - High
- March 24, 2026
Incorrect boundary conditions in the Audio/Video: Web Codecs component. This vulnerability affects Firefox < 149, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
Improper Check for Unusual or Exceptional Conditions
UA-Free in Firefox Layout:Text & Fonts v<149 (ESR<115.34)
CVE-2026-4696
9.8 - Critical
- March 24, 2026
Use-after-free in the Layout: Text and Fonts component. This vulnerability affects Firefox < 149, Firefox ESR < 115.34, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
Dangling pointer
Firefox <149: Incorrect Boundary Conditions in Audio/Video Web Codecs
CVE-2026-4695
7.5 - High
- March 24, 2026
Incorrect boundary conditions in the Audio/Video: Web Codecs component. This vulnerability affects Firefox < 149, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
Improper Check for Unusual or Exceptional Conditions
Integer Overflow Firefox Graphics <=149 (ESR<115.34)
CVE-2026-4694
7.5 - High
- March 24, 2026
Incorrect boundary conditions, integer overflow in the Graphics component. This vulnerability affects Firefox < 149, Firefox ESR < 115.34, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
Improper Check for Unusual or Exceptional Conditions
Firefox <149/ESR<140.9 AV Playback Boundary Check Failure
CVE-2026-4693
7.5 - High
- March 24, 2026
Incorrect boundary conditions in the Audio/Video: Playback component. This vulnerability affects Firefox < 149, Firefox ESR < 115.34, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
Improper Check for Unusual or Exceptional Conditions
CVE-2026-4692: Sandbox Escape via Responsive Design Mode in Firefox <149
CVE-2026-4692
9.6 - Critical
- March 24, 2026
Sandbox escape in the Responsive Design Mode component. This vulnerability affects Firefox < 149, Firefox ESR < 115.34, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
Firefox CSS Parsing Use-After-Free (before 149, ESR <115.34/140.9)
CVE-2026-4691
9.8 - Critical
- March 24, 2026
Use-after-free in the CSS Parsing and Computation component. This vulnerability affects Firefox < 149, Firefox ESR < 115.34, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
Dangling pointer
Firefox <149 XPCOM Sandbox Escape (CVE-2026-4690)
CVE-2026-4690
9.6 - Critical
- March 24, 2026
Sandbox escape due to incorrect boundary conditions, integer overflow in the XPCOM component. This vulnerability affects Firefox < 149, Firefox ESR < 115.34, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
Integer Overflow or Wraparound
Firefox <149 Sandbox Escape: XPCOM Integer Overflow
CVE-2026-4689
10 - Critical
- March 24, 2026
Sandbox escape due to incorrect boundary conditions, integer overflow in the XPCOM component. This vulnerability affects Firefox < 149, Firefox ESR < 115.34, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
Classic Buffer Overflow
Firefox <149/ESR<140.9: Disability Access API UAF Sandbox Escape
CVE-2026-4688
9.6 - Critical
- March 24, 2026
Sandbox escape due to use-after-free in the Disability Access APIs component. This vulnerability affects Firefox < 149, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
Dangling pointer
Firefox <149 Sandbox Escape via Telemetry Boundary Conditions
CVE-2026-4687
9.6 - Critical
- March 24, 2026
Sandbox escape due to incorrect boundary conditions in the Telemetry component. This vulnerability affects Firefox < 149, Firefox ESR < 115.34, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
Classic Buffer Overflow
Firefox Canvas2D Incorrect Boundary Conditions ( Firefox 149 / ESR 140.9)
CVE-2026-4686
7.5 - High
- March 24, 2026
Incorrect boundary conditions in the Graphics: Canvas2D component. This vulnerability affects Firefox < 149, Firefox ESR < 115.34, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
Improper Check for Unusual or Exceptional Conditions
Firefox Canvas2D boundary flaw before v149/ESR115.34/ESR140.9
CVE-2026-4685
7.5 - High
- March 24, 2026
Incorrect boundary conditions in the Graphics: Canvas2D component. This vulnerability affects Firefox < 149, Firefox ESR < 115.34, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
Improper Check for Unusual or Exceptional Conditions
WebRender Use-After-Free Race in Firefox <149 (ESR <115.34/140.9)
CVE-2026-4684
7.5 - High
- March 24, 2026
Race condition, use-after-free in the Graphics: WebRender component. This vulnerability affects Firefox < 149, Firefox ESR < 115.34, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
Dangling pointer
Memory Safety Bugs in Firefox 147 (CVE20262807)
CVE-2026-2807
9.8 - Critical
- February 24, 2026
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 affects Firefox < 148 and Thunderbird < 148.
Memory Corruption
Invalid pointer DOM Core & HTML in Firefox <148
CVE-2026-2805
9.8 - Critical
- February 24, 2026
Invalid pointer in the DOM: Core & HTML component. This vulnerability affects Firefox < 148 and Thunderbird < 148.
Access of Uninitialized Pointer
Firefox Graphics Text Uninit Memory (CVE-2026-2806)
CVE-2026-2806
9.1 - Critical
- February 24, 2026
Uninitialized memory in the Graphics: Text component. This vulnerability affects Firefox < 148 and Thunderbird < 148.
Use of Uninitialized Variable
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