SB2026051930 - Multiple vulnerabilities in Mozilla Firefox ESR 140

Description

This security bulletin contains information about 20 vulnerabilities.

1) Improper privilege management (CVE-ID: CVE-2026-8957)

CWE-ID: CWE-269 - Improper Privilege Management

CVSSv4: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear

The vulnerability allows a local user to escalate privileges.

The vulnerability exists due to improper access control in the Enterprise Policies component when modifying enterprise policy handling. A local user can manipulate enterprise policy behavior to escalate privileges.

2) Integer overflow (CVE-ID: CVE-2026-8956)

CWE-ID: CWE-190 - Integer overflow

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.

The vulnerability exists due to integer overflow in the Networking: JAR component when processing crafted web content. A remote attacker can supply crafted content to cause a denial of service.

User interaction is required to visit a specially crafted website or URL.

3) Buffer overflow (CVE-ID: CVE-2026-8974)

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 unspecified components when processing crafted web content. A remote attacker can trigger memory corruption to execute arbitrary code.

Some of the bugs showed evidence of memory corruption.

4) Improper privilege management (CVE-ID: CVE-2026-8970)

CWE-ID: CWE-269 - Improper Privilege Management

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 escalate privileges.

The vulnerability exists due to improper access control in the Security component when processing crafted web content. A remote attacker can trigger the flaw to escalate privileges.

User interaction is required to visit a specially crafted website or URL.

5) NULL pointer dereference (CVE-ID: CVE-2026-8968)

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.

The vulnerability exists due to an invalid pointer dereference in the Audio/Video: Web Codecs component when processing crafted web content. A remote attacker can trigger the invalid pointer condition to cause a denial of service.

User interaction is required to visit a specially crafted website or URL.

6) Protection Mechanism Failure (CVE-ID: CVE-2026-8962)

CWE-ID: CWE-693 - Protection Mechanism Failure

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 a security mitigation.

The vulnerability exists due to improper access control in the DOM: Security component when processing crafted web content. A remote attacker can trigger the flaw to bypass a security mitigation.

User interaction is required to visit a specially crafted website or URL.

7) Input validation error (CVE-ID: CVE-2026-8961)

CWE-ID: CWE-20 - Improper input validation

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 spoof content.

The vulnerability exists due to improper input validation in the Form Autofill component when rendering crafted web content. A remote attacker can present crafted content to spoof content.

User interaction is required to visit a specially crafted website or URL.

8) Out-of-bounds read (CVE-ID: CVE-2026-8959)

CWE-ID: CWE-125 - Out-of-bounds read

CVSSv4: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear

The vulnerability allows a local user to escape the sandbox.

The vulnerability exists due to incorrect boundary conditions in the Widget: Win32 component when handling local interaction with the application. A local user can trigger the flaw to escape the sandbox.

The issue affects the Win32-specific component.

9) Improper access control (CVE-ID: CVE-2026-8958)

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 disclose sensitive information and escape the sandbox.

The vulnerability exists due to improper access control in the Security: Process Sandboxing component when processing crafted web content. A remote attacker can trigger the flaw to disclose sensitive information and escape the sandbox.

User interaction is required to visit a specially crafted website or URL.

10) Out-of-bounds read (CVE-ID: CVE-2026-8946)

CWE-ID: CWE-125 - Out-of-bounds read

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 incorrect boundary conditions in the Audio/Video: Web Codecs component when processing crafted web content. A remote attacker can cause the browser to process specially crafted content to execute arbitrary code.

User interaction is required to visit a specially crafted website or URL.

11) Improper privilege management (CVE-ID: CVE-2026-8955)

CWE-ID: CWE-269 - Improper Privilege Management

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 escalate privileges.

The vulnerability exists due to improper access control in the DOM: Workers component when processing crafted web content. A remote attacker can trigger the flaw to escalate privileges.

User interaction is required to visit a specially crafted website or URL.

12) Integer overflow (CVE-ID: CVE-2026-8954)

CWE-ID: CWE-190 - Integer overflow

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.

The vulnerability exists due to incorrect boundary conditions and integer overflow in the Audio/Video component when processing crafted media content. A remote attacker can supply crafted media content to cause a denial of service.

User interaction is required to visit a specially crafted website or URL.

13) Use-after-free (CVE-ID: CVE-2026-8953)

CWE-ID: CWE-416 - Use After Free

CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:U/U:Green

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 processing crafted web content. A remote attacker can trigger the flaw to escape the sandbox.

User interaction is required to visit a specially crafted website or URL.

14) Improper access control (CVE-ID: CVE-2026-8950)

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: HTTP component when handling crafted web content. A remote attacker can cause the browser to process crafted content to bypass the same-origin policy.

User interaction is required to visit a specially crafted website or URL.

15) Integer overflow (CVE-ID: CVE-2026-8949)

CWE-ID: CWE-190 - Integer overflow

CVSSv4: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear

The vulnerability allows a local user to execute arbitrary code.

The vulnerability exists due to integer overflow in the Widget: Win32 component when handling local interaction with the application. A local user can trigger the integer overflow to execute arbitrary code.

The issue affects the Win32-specific component.

16) Protection mechanism failure (CVE-ID: CVE-2026-8401)

CWE-ID: CWE-693 - Protection Mechanism Failure

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 bypass implemented security restrictions.

The vulnerability exists due to insufficient implementation of security measures in the Profile Backup component. An attacker can trick the victim into visiting a specially crafted website and bypass sandbox restrictions, leading to remote code execution. 

17) Input validation error (CVE-ID: CVE-2026-8391)

CWE-ID: CWE-20 - Improper input validation

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 compromise the affected system.

The vulnerability exists due to an unspecified issue in the JavaScript Engine component. A remote attacker can trick the victim into visiting a specially crafted website and execute arbitrary code on the system.

18) Use-after-free (CVE-ID: CVE-2026-8947)

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 DOM: Bindings (WebIDL) component when processing crafted web content. A remote attacker can cause the browser to process specially crafted content to execute arbitrary code.

User interaction is required to visit a specially crafted website or URL.

19) Input validation error (CVE-ID: CVE-2026-8388)

CWE-ID: CWE-20 - Improper input validation

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 improper input validation in the JavaScript Engine: JIT component when processing crafted JavaScript. A remote attacker can supply specially crafted script content to execute arbitrary code.

20) Buffer overflow (CVE-ID: CVE-2026-8975)

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 web content. A remote attacker can cause the browser to process specially crafted content to execute arbitrary code.

User interaction is required to visit a specially crafted website or URL.

Remediation

Install update from vendor's website.

References

• https://www.mozilla.org/en-US/security/advisories/mfsa2026-48/