SB2026072301 - Multiple vulnerabilities in Mozilla Thunderbird ESR
Published: July 23, 2026
Breakdown by Severity
- Low
- Medium
- High
- Critical
Description
This security bulletin contains information about 33 vulnerabilities.
1) Protection mechanism failure (CVE-ID: CVE-2026-16390)
CWE-ID: CWE-693 - Protection Mechanism Failure
CVSSv4: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/U:Green
The vulnerability allows a remote attacker to bypass a security restriction.
The vulnerability exists due to a mitigation bypass in the Enterprise Policies component when applying enterprise policies. A remote attacker can trigger crafted policy conditions to bypass a security restriction.
2) Information disclosure (CVE-ID: CVE-2026-16374)
CWE-ID: CWE-200 - Exposure of sensitive information to an unauthorized actor
CVSSv4: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:U/U:Green
The vulnerability allows a remote attacker to disclose sensitive information.
The vulnerability exists due to an information disclosure flaw in the Framework component in DevTools when using developer tools functionality. A remote attacker can trigger the flaw through crafted developer tools interactions to disclose sensitive information.
3) Protection mechanism failure (CVE-ID: CVE-2026-16375)
CWE-ID: CWE-693 - Protection Mechanism Failure
CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/U:Amber
The vulnerability allows a remote attacker to bypass site isolation.
The vulnerability exists due to a site isolation issue in the Networking: HTTP component when handling HTTP traffic. A remote attacker can trigger crafted HTTP behavior to bypass site isolation.
4) Protection mechanism failure (CVE-ID: CVE-2026-16377)
CWE-ID: CWE-693 - Protection Mechanism Failure
CVSSv4: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/U:Green
The vulnerability allows a remote attacker to bypass a security restriction.
The vulnerability exists due to a mitigation bypass in the PDF Viewer component when rendering PDF content. A remote attacker can supply crafted PDF content to bypass a security restriction.
5) Improper privilege management (CVE-ID: CVE-2026-16379)
CWE-ID: CWE-269 - Improper Privilege Management
CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:L/VI:H/VA:N/SC:N/SI:N/SA:N/E:U/U:Amber
The vulnerability allows a remote attacker to escalate privileges.
The vulnerability exists due to improper access control in the DOM: Content Processes component when handling content processes. A remote attacker can trigger crafted content process behavior to escalate privileges.
6) Improper access control (CVE-ID: CVE-2026-16358)
CWE-ID: CWE-284 - Improper Access Control
CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/U:Green
The vulnerability allows a remote attacker to bypass site isolation.
The vulnerability exists due to a site isolation issue in the Graphics: WebRender component when rendering content. A remote attacker can convince the victim to visit a specially crafted website or URL to bypass site isolation.
7) Improper access control (CVE-ID: CVE-2026-16381)
CWE-ID: CWE-284 - Improper Access Control
CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/U:Amber
The vulnerability allows a remote attacker to bypass the same-origin policy.
The vulnerability exists due to improper access control in the Networking: DNS component when resolving DNS requests. A remote attacker can trigger crafted DNS behavior to bypass the same-origin policy.
8) Protection mechanism failure (CVE-ID: CVE-2026-16383)
CWE-ID: CWE-693 - Protection Mechanism Failure
CVSSv4: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/U:Green
The vulnerability allows a remote attacker to bypass a security restriction.
The vulnerability exists due to a mitigation bypass in the DOM: Networking component when handling network operations. A remote attacker can trigger crafted network behavior to bypass a security restriction.
9) Protection mechanism failure (CVE-ID: CVE-2026-16387)
CWE-ID: CWE-693 - Protection Mechanism Failure
CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/U:Amber
The vulnerability allows a remote attacker to bypass site isolation.
The vulnerability exists due to a site isolation issue in the Networking component when handling network operations. A remote attacker can trigger crafted network behavior to bypass site isolation.
10) Improper privilege management (CVE-ID: CVE-2026-16371)
CWE-ID: CWE-269 - Improper Privilege Management
CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:L/VI:H/VA:N/SC:N/SI:N/SA:N/E:U/U:Amber
The vulnerability allows a remote attacker to escalate privileges.
The vulnerability exists due to improper access control in the DOM: Navigation component when handling navigation operations. A remote attacker can trigger crafted navigation behavior to escalate privileges.
11) Information disclosure (CVE-ID: CVE-2026-16391)
CWE-ID: CWE-200 - Exposure of sensitive information to an unauthorized actor
CVSSv4: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:U/U:Green
The vulnerability allows a remote attacker to disclose sensitive information.
The vulnerability exists due to an information disclosure flaw in the Storage: IndexedDB component when handling stored web data. A remote attacker can trigger crafted storage interactions to disclose sensitive information.
12) Input validation error (CVE-ID: CVE-2026-16359)
CWE-ID: CWE-20 - Improper input validation
CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green
The vulnerability allows a remote attacker to cause a denial of service or execute arbitrary code.
The vulnerability exists due to incorrect boundary conditions in the Audio/Video: GMP component when processing media content. A remote attacker can convince the victim to visit a specially crafted website or URL to cause a denial of service or execute arbitrary code.
13) Improper privilege management (CVE-ID: CVE-2026-16396)
CWE-ID: CWE-269 - Improper Privilege Management
CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:H/VA:N/SC:N/SI:N/SA:N/E:U/U:Green
The vulnerability allows a remote user to escalate privileges.
The vulnerability exists due to improper access control in WebExtensions when using extension functionality. A remote user can abuse extension functionality to escalate privileges.
Exploitation requires the use of WebExtensions.
14) Information disclosure (CVE-ID: CVE-2026-16405)
CWE-ID: CWE-200 - Exposure of sensitive information to an unauthorized actor
CVSSv4: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:U/U:Clear
The vulnerability allows a remote attacker to disclose sensitive information.
The vulnerability exists due to an information disclosure flaw in the Networking: WebSockets component when handling WebSocket connections. A remote attacker can trigger crafted WebSocket behavior to disclose sensitive information.
15) Buffer overflow (CVE-ID: CVE-2026-16412)
CWE-ID: CWE-119 - Memory corruption
CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Amber
The vulnerability allows a remote attacker to execute arbitrary code.
The vulnerability exists due to memory corruption in multiple components when processing crafted content. A remote attacker can trigger memory corruption using crafted content to execute arbitrary code.
Mozilla reported that some of the underlying bugs showed evidence of memory corruption.
16) Buffer overflow (CVE-ID: CVE-2026-16360)
CWE-ID: CWE-119 - Memory corruption
CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Amber
The vulnerability allows a remote attacker to execute arbitrary code.
The vulnerability exists due to memory corruption in multiple components when processing web content. A remote attacker can convince the victim to visit a specially crafted website or URL to execute arbitrary code.
Some of the underlying bugs showed evidence of memory corruption.
17) Buffer overflow (CVE-ID: CVE-2026-16361)
CWE-ID: CWE-119 - Memory corruption
CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Amber
The vulnerability allows a remote attacker to execute arbitrary code.
The vulnerability exists due to memory corruption in multiple components when processing web content. A remote attacker can convince the victim to visit a specially crafted website or URL to execute arbitrary code.
Some of the underlying bugs showed evidence of memory corruption.
18) Off-by-one (CVE-ID: CVE-2026-14899)
CWE-ID: CWE-193 - Off-by-one Error
CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N/E:U/U:Green
The vulnerability allows a remote attacker to gain access to sensitive information.
The vulnerability exists due to an off-by-one error within the MIME header parser. A remote attacker can trick the victim into opening a specially crafted email and read contents of memory on the system or crash the application.
19) Input validation error (CVE-ID: CVE-2026-16357)
CWE-ID: CWE-20 - Improper input validation
CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green
The vulnerability allows a remote attacker to cause a denial of service or execute arbitrary code.
The vulnerability exists due to incorrect boundary conditions in the Graphics component when processing rendered content. A remote attacker can convince the victim to visit a specially crafted website or URL to cause a denial of service or execute arbitrary code.
20) Use-after-free (CVE-ID: CVE-2026-16356)
CWE-ID: CWE-416 - Use After Free
CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Amber
The vulnerability allows a remote attacker to escape the sandbox.
The vulnerability exists due to use-after-free in the Disability Access APIs component when interacting with accessibility functionality. A remote attacker can convince the victim to visit a specially crafted website or URL to escape the sandbox.
21) Incorrect calculation (CVE-ID: CVE-2026-16355)
CWE-ID: CWE-682 - Incorrect Calculation
CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Amber
The vulnerability allows a remote attacker to execute arbitrary code.
The vulnerability exists due to JIT miscompilation in the JavaScript Engine: JIT component when executing script content. A remote attacker can convince the victim to visit a specially crafted website or URL to execute arbitrary code.
22) Integer overflow (CVE-ID: CVE-2026-16369)
CWE-ID: CWE-190 - Integer overflow
CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Amber
The vulnerability allows a remote attacker to execute arbitrary code.
The vulnerability exists due to integer overflow in the JavaScript: WebAssembly component when compiling or executing WebAssembly content. A remote attacker can supply crafted WebAssembly content to execute arbitrary code.
23) Out-of-bounds read (CVE-ID: CVE-2026-16368)
CWE-ID: CWE-125 - Out-of-bounds read
CVSSv4: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to incorrect boundary conditions in the JavaScript: WebAssembly component when compiling or executing WebAssembly content. A remote attacker can supply crafted WebAssembly content to cause a denial of service.
24) Information disclosure (CVE-ID: CVE-2026-16354)
CWE-ID: CWE-200 - Exposure of sensitive information to an unauthorized actor
CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:U/U:Green
The vulnerability allows a remote attacker to disclose sensitive information.
The vulnerability exists due to improper access control in the Graphics: ImageLib component when processing image content. A remote attacker can convince the victim to visit a specially crafted website or URL to disclose sensitive information.
25) NULL pointer dereference (CVE-ID: CVE-2026-16353)
CWE-ID: CWE-476 - NULL Pointer Dereference
CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green
The vulnerability allows a remote attacker to cause a denial of service or execute arbitrary code.
The vulnerability exists due to an invalid pointer in the DOM: Bindings (WebIDL) component when processing web content. A remote attacker can convince the victim to visit a specially crafted website or URL to cause a denial of service or execute arbitrary code.
26) Incorrect calculation (CVE-ID: CVE-2026-16363)
CWE-ID: CWE-682 - Incorrect Calculation
CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Amber
The vulnerability allows a remote attacker to execute arbitrary code.
The vulnerability exists due to JIT miscompilation in the JavaScript: WebAssembly component when compiling and executing WebAssembly content. A remote attacker can supply crafted WebAssembly content to execute arbitrary code.
27) Use-after-free (CVE-ID: CVE-2026-16352)
CWE-ID: CWE-416 - Use After Free
CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Amber
The vulnerability allows a remote attacker to escape the sandbox.
The vulnerability exists due to use-after-free in the Disability Access APIs component when interacting with accessibility functionality. A remote attacker can convince the victim to visit a specially crafted website or URL to escape the sandbox.
28) Use-after-free (CVE-ID: CVE-2026-16351)
CWE-ID: CWE-416 - Use After Free
CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Amber
The vulnerability allows a remote attacker to escape the sandbox.
The vulnerability exists due to use-after-free in the DOM: Navigation component when handling navigation. A remote attacker can convince the victim to visit a specially crafted website or URL to escape the sandbox.
29) Use-after-free (CVE-ID: CVE-2026-16362)
CWE-ID: CWE-416 - Use After Free
CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Amber
The vulnerability allows a remote attacker to execute arbitrary code.
The vulnerability exists due to use-after-free in the WebRTC: Audio/Video component when processing real-time audio or video content. A remote attacker can trigger the flaw using crafted real-time media interactions to execute arbitrary code.
30) Input validation error (CVE-ID: CVE-2026-16350)
CWE-ID: CWE-20 - Improper input validation
CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green
The vulnerability allows a remote attacker to cause a denial of service or execute arbitrary code.
The vulnerability exists due to incorrect boundary conditions in the Audio/Video: cubeb component when processing media content. A remote attacker can convince the victim to visit a specially crafted website or URL to cause a denial of service or execute arbitrary code.
31) Improper access control (CVE-ID: CVE-2026-16349)
CWE-ID: CWE-284 - Improper Access Control
CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/U:Green
The vulnerability allows a remote attacker to bypass the same-origin policy.
The vulnerability exists due to improper access control in the DOM: Navigation component when handling navigation. A remote attacker can convince the victim to visit a specially crafted website or URL to bypass the same-origin policy.
32) Improper access control (CVE-ID: CVE-2026-15719)
CWE-ID: CWE-284 - Improper Access Control
CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:U/U:Amber
The vulnerability allows a remote attacker to manipulate DOM elements.
The vulnerability exists due to improper access restrictions within the Navigation component. A remote attacker can trick the victim into visiting a specially crafted website and manipulate arbitrary DOM object, bypassing site isolation in DOM.
33) Access of Uninitialized Pointer (CVE-ID: CVE-2026-15718)
CWE-ID: CWE-824 - Access of Uninitialized Pointer
CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Amber
The vulnerability allows a remote attacker to execute arbitrary code.
The vulnerability exists due to an invalid pointer in the JavaScript: WebAssembly component when processing web content. A remote attacker can trigger the vulnerable component to execute arbitrary code.
Remediation
Install update from vendor's website.