Site Isolation Flaw in Firefox Graphics Component
CVE-2026-74970

5.4MEDIUM

Key Information:

Vendor

Mozilla
Status
Firefox
Thunderbird
Vendor
CVE Published:
18 August 2026

Badges

👾 Exploit Exists🟡 Public PoC

What is CVE-2026-74970?

A site isolation vulnerability exists in the Graphics component of Mozilla Firefox, which could allow attackers to execute unauthorized actions across different sites. This issue has been addressed in Firefox version 154 and Firefox Extended Support Release (ESR) version 153.1, enhancing user security and preventing cross-site risks.

Affected Version(s)

Firefox 153.1

Firefox 154

Thunderbird 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.

Trespasser
Created by defineid

References

https://bugzilla.mozilla.org/show_bug.cgi?id=2056558
https://www.mozilla.org/security/advisories/mfsa2026-74/
https://www.mozilla.org/security/advisories/mfsa2026-77/

CVSS V3.1

Score:
5.4
Severity:
MEDIUM
Confidentiality:
Low
Integrity:
Low
Availability:
Low
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

Abdulaziz Alasaiqah
.