Privilege Escalation Vulnerability in Mozilla Firefox Navigation Component
CVE-2026-74939

8.8HIGH

Key Information:

Vendor

Mozilla
Status
Firefox
Thunderbird
Vendor
CVE Published:
18 August 2026

Badges

👾 Exploit Exists🟡 Public PoC

What is CVE-2026-74939?

A security flaw in the Mozilla Firefox navigation component allows unauthorized users to escalate their privileges, potentially exposing critical parts of the application. This vulnerability was addressed in multiple versions, including Firefox 154 and various releases of Firefox ESR. Users are strongly encouraged to update their browsers to mitigate the risk associated with this issue.

Affected Version(s)

Firefox 115.39

Firefox 140.14

Firefox 153.1

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-2026-74939-escape-the-mac-n-cheese-box
Created by SneakyNachos

References

https://bugzilla.mozilla.org/show_bug.cgi?id=2054416
https://www.mozilla.org/security/advisories/mfsa2026-74/
https://www.mozilla.org/security/advisories/mfsa2026-75/

CVSS V3.1

Score:
8.8
Severity:
HIGH
Confidentiality:
High
Integrity:
High
Availability:
High
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
Required
Scope:
Unchanged

Timeline

  • 🟡

    Public PoC available

  • 👾

    Exploit known to exist

  • Vulnerability published

  • Vulnerability Reserved

Credit

choeseyeong
.