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Firefox and Thunderbird Security Update: Multiple Vulnerabilities

OESA-2026-1540
Summary

Mozilla has released a security update for Firefox and Thunderbird to fix multiple vulnerabilities that could allow an attacker to take control of your computer or access sensitive information. If you use either of these programs, it's essential to update to the latest version to protect your data and computer. If you're not sure how to update, check the software's settings or contact your IT department for assistance.

What to do
  • Update thunderbird to version 140.8.0-1.oe2403sp3.
Affected software
VendorProductAffected versionsFix available
– thunderbird <= 140.8.0-1.oe2403sp3 140.8.0-1.oe2403sp3
Original title
thunderbird security update
Original description
Mozilla Thunderbird is a standalone mail and newsgroup client.

Security Fix(es):

Incorrect boundary conditions in the WebRTC: Audio/Video component. This vulnerability affects Firefox &lt; 148, Firefox ESR &lt; 115.33, Firefox ESR &lt; 140.8, Thunderbird &lt; 148, and Thunderbird &lt; 140.8.(CVE-2026-2757)

Use-after-free in the JavaScript: GC component. This vulnerability affects Firefox &lt; 148, Firefox ESR &lt; 115.33, Firefox ESR &lt; 140.8, Thunderbird &lt; 148, and Thunderbird &lt; 140.8.(CVE-2026-2758)

Incorrect boundary conditions in the Graphics: ImageLib component. This vulnerability affects Firefox &lt; 148, Firefox ESR &lt; 115.33, Firefox ESR &lt; 140.8, Thunderbird &lt; 148, and Thunderbird &lt; 140.8.(CVE-2026-2759)

Sandbox escape due to incorrect boundary conditions in the Graphics: WebRender component. This vulnerability affects Firefox &lt; 148, Firefox ESR &lt; 115.33, Firefox ESR &lt; 140.8, Thunderbird &lt; 148, and Thunderbird &lt; 140.8.(CVE-2026-2760)

Sandbox escape in the Graphics: WebRender component. This vulnerability affects Firefox &lt; 148, Firefox ESR &lt; 115.33, Firefox ESR &lt; 140.8, Thunderbird &lt; 148, and Thunderbird &lt; 140.8.(CVE-2026-2761)

Integer overflow in the JavaScript: Standard Library component. This vulnerability affects Firefox &lt; 148, Firefox ESR &lt; 140.8, Thunderbird &lt; 148, and Thunderbird &lt; 140.8.(CVE-2026-2762)

Use-after-free in the JavaScript Engine component. This vulnerability affects Firefox &lt; 148, Firefox ESR &lt; 115.33, Firefox ESR &lt; 140.8, Thunderbird &lt; 148, and Thunderbird &lt; 140.8.(CVE-2026-2763)

JIT miscompilation, use-after-free in the JavaScript Engine: JIT component. This vulnerability affects Firefox &lt; 148, Firefox ESR &lt; 115.33, Firefox ESR &lt; 140.8, Thunderbird &lt; 148, and Thunderbird &lt; 140.8.(CVE-2026-2764)

Use-after-free in the JavaScript Engine component. This vulnerability affects Firefox &lt; 148, Firefox ESR &lt; 140.8, Thunderbird &lt; 148, and Thunderbird &lt; 140.8.(CVE-2026-2765)

Use-after-free in the JavaScript Engine: JIT component. This vulnerability affects Firefox &lt; 148, Firefox ESR &lt; 140.8, Thunderbird &lt; 148, and Thunderbird &lt; 140.8.(CVE-2026-2766)

Use-after-free in the JavaScript: WebAssembly component. This vulnerability affects Firefox &lt; 148, Firefox ESR &lt; 140.8, Thunderbird &lt; 148, and Thunderbird &lt; 140.8.(CVE-2026-2767)

Sandbox escape in the Storage: IndexedDB component. This vulnerability affects Firefox &lt; 148, Firefox ESR &lt; 140.8, Thunderbird &lt; 148, and Thunderbird &lt; 140.8.(CVE-2026-2768)

Use-after-free in the Storage: IndexedDB component. This vulnerability affects Firefox &lt; 148, Firefox ESR &lt; 115.33, Firefox ESR &lt; 140.8, Thunderbird &lt; 148, and Thunderbird &lt; 140.8.(CVE-2026-2769)

Use-after-free in the DOM: Bindings (WebIDL) component. This vulnerability affects Firefox &lt; 148, Firefox ESR &lt; 115.33, Firefox ESR &lt; 140.8, Thunderbird &lt; 148, and Thunderbird &lt; 140.8.(CVE-2026-2770)

Undefined behavior in the DOM: Core &amp; HTML component. This vulnerability affects Firefox &lt; 148, Firefox ESR &lt; 115.33, Firefox ESR &lt; 140.8, Thunderbird &lt; 148, and Thunderbird &lt; 140.8.(CVE-2026-2771)

Use-after-free in the Audio/Video: Playback component. This vulnerability affects Firefox &lt; 148, Firefox ESR &lt; 115.33, Firefox ESR &lt; 140.8, Thunderbird &lt; 148, and Thunderbird &lt; 140.8.(CVE-2026-2772)

Incorrect boundary conditions in the Web Audio component. This vulnerability affects Firefox &lt; 148, Firefox ESR &lt; 115.33, Firefox ESR &lt; 140.8, Thunderbird &lt; 148, and Thunderbird &lt; 140.8.(CVE-2026-2773)

Integer overflow in the Audio/Video component. This vulnerability affects Firefox &lt; 148, Firefox ESR &lt; 115.33, Firefox ESR &lt; 140.8, Thunderbird &lt; 148, and Thunderbird &lt; 140.8.(CVE-2026-2774)

Mitigation bypass in the DOM: HTML Parser component. This vulnerability affects Firefox &lt; 148, Firefox ESR &lt; 115.33, Firefox ESR &lt; 140.8, Thunderbird &lt; 148, and Thunderbird &lt; 140.8.(CVE-2026-2775)

Privilege escalation in the Messaging System component. This vulnerability affects Firefox &lt; 148, Firefox ESR &lt; 115.33, Firefox ESR &lt; 140.8, Thunderbird &lt; 148, and Thunderbird &lt; 140.8.(CVE-2026-2777)

Sandbox escape due to incorrect boundary conditions in the DOM: Core &amp; HTML component. This vulnerability affects Firefox &lt; 148, Firefox ESR &lt; 115.33, Firefox ESR &lt; 140.8, Thunderbird &lt; 148, and Thunderbird &lt; 140.8.(CVE-2026-2778)

Incorrect boundary conditions in the Networking: JAR component. This vulnerability affects Firefox &lt; 148, Firefox ESR &lt; 140.8, Thunderbird &lt; 148, and Thunderbird &lt; 140.8.(CVE-2026-2779)

Integer overflow in the Libraries component in NSS. This vulnerability affects Firefox &lt; 148, Firefox ESR &lt; 140.8, Thunderbird &lt; 148, and Thunderbird &lt; 140.8.(CVE-2026-2781)

Privilege escalation in the Netmonitor component. This vulnerability affects Firefox &lt; 148, Firefox ESR &lt; 140.8, Thunderbird &lt; 148, and Thunderbird &lt; 140.8.(CVE-2026-2782)

Information disclosure due to JIT miscompilation in the JavaScript Engine: JIT component. This vulnerability affects Firefox &lt; 148, Firefox ESR &lt; 140.8, Thunderbird &lt; 148, and Thunderbird &lt; 140.8.(CVE-2026-2783)

Mitigation bypass in the DOM: Security component. This vulnerability affects Firefox &lt; 148, Firefox ESR &lt; 140.8, Thunderbird &lt; 148, and Thunderbird &lt; 140.8.(CVE-2026-2784)

Invalid pointer in the JavaScript Engine component. This vulnerability affects Firefox &lt; 148, Firefox ESR &lt; 140.8, Thunderbird &lt; 148, and Thunderbird &lt; 140.8.(CVE-2026-2785)

Use-after-free in the JavaScript Engine component. This vulnerability affects Firefox &lt; 148, Firefox ESR &lt; 140.8, Thunderbird &lt; 148, and Thunderbird &lt; 140.8.(CVE-2026-2786)

Use-after-free in the DOM: Window and Location component. This vulnerability affects Firefox &lt; 148, Firefox ESR &lt; 115.33, Firefox ESR &lt; 140.8, Thunderbird &lt; 148, and Thunderbird &lt; 140.8.(CVE-2026-2787)

Incorrect boundary conditions in the Audio/Video: GMP component. This vulnerability affects Firefox &lt; 148, Firefox ESR &lt; 115.33, Firefox ESR &lt; 140.8, Thunderbird &lt; 148, and Thunderbird &lt; 140.8.(CVE-2026-2788)

Use-after-free in the Graphics: ImageLib component. This vulnerability affects Firefox &lt; 148, Firefox ESR &lt; 115.33, Firefox ESR &lt; 140.8, Thunderbird &lt; 148, and Thunderbird &lt; 140.8.(CVE-2026-2789)

Same-origin policy bypass in the Networking: JAR component. This vulnerability affects Firefox &lt; 148, Firefox ESR &lt; 140.8, Thunderbird &lt; 148, and Thunderbird &lt; 140.8.(CVE-2026-2790)

Mitigation bypass in the Networking: Cache component. This vulnerability affects Firefox &lt; 148, Firefox ESR &lt; 140.8, Thunderbird &lt; 148, and Thunderbird &lt; 140.8.(CVE-2026-2791)

Memory safety bugs present in Firefox ESR 140.7, Thunderbird ESR 140.7, 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 &lt; 148, Firefox ESR &lt; 140.8, Thunderbird &lt; 148, and Thunderbird &lt; 140.8.(CVE-2026-2792)

Memory safety bugs present in Firefox ESR 115.32, Firefox ESR 140.7, Thunderbird ESR 140.7, 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 &lt; 148, Firefox ESR &lt; 115.33, Firefox ESR &lt; 140.8, Thunderbird &lt; 148, and Thunderbird &lt; 140.8.(CVE-2026-2793)
Published: 6 Mar 2026 · Updated: 6 Mar 2026 · First seen: 6 Mar 2026