Use-After-Free Vulnerability in Firefox Browser by Mozilla
CVE-2026-2766

9.8CRITICAL

Key Information:

Vendor

Mozilla
Status
Firefox
Thunderbird
Vendor
CVE Published:
24 February 2026

Badges

👾 Exploit Exists🟡 Public PoC

What is CVE-2026-2766?

A use-after-free vulnerability has been identified in the JIT component of the JavaScript engine within Mozilla's Firefox browser. This flaw can lead to memory corruption issues, potentially allowing attackers to execute arbitrary code or cause unexpected behavior in affected Firefox versions, specifically those prior to 148 and Firefox ESR versions prior to 140.8. Users are advised to keep their browsers updated to the latest versions to mitigate these risks.

Affected Version(s)

Firefox 140.8

Firefox 148

Thunderbird 140.8

Exploit Proof of Concept (PoC)

PoC code is written by security researchers to demonstrate the vulnerability can be exploited. PoC code is also a key component for weaponization which could lead to ransomware.

CVE-2026-2766-but-with-wasm
Created by SneakyNachos

References

https://bugzilla.mozilla.org/show_bug.cgi?id=2013583
https://www.mozilla.org/security/advisories/mfsa2026-13/
https://www.mozilla.org/security/advisories/mfsa2026-15/

CVSS V3.1

Score:
9.8
Severity:
CRITICAL
Confidentiality:
High
Integrity:
High
Availability:
High
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • 🟡

    Public PoC available

  • 👾

    Exploit known to exist

  • Vulnerability published

  • Vulnerability Reserved

Credit

Information to follow
.