Cyber Posture

CVE-2026-6768

Critical

Published: 21 April 2026

Published
21 April 2026
Modified
22 April 2026
KEV Added
—
Patch
—
CVSS Score 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS Score 0.0005 17.0th percentile
Risk Priority 20 60% EPSS · 20% KEV · 20% CVSS

Description

Mitigation bypass in the Networking: Cookies component. This vulnerability was fixed in Firefox 150 and Thunderbird 150.

Mitigating Controls (NIST 800-53 r5)AI

SI-2 Flaw Remediation good match
prevent

Directly mandates identification, reporting, and correction of the mitigation bypass flaw in Firefox and Thunderbird's Networking: Cookies component via patching to version 150.

SI-5 Security Alerts, Advisories, and Directives good match
prevent

Requires obtaining and disseminating security advisories such as Mozilla's MFSA2026-30 and MFSA2026-33 to enable timely patching of the cookie handling vulnerability.

RA-5 Vulnerability Monitoring and Scanning partial match
detect

Vulnerability scanning detects systems running vulnerable versions of Firefox or Thunderbird affected by CVE-2026-6768.

Security SummaryAI

CVE-2026-6768 is a mitigation bypass vulnerability in the Networking: Cookies component of Mozilla Firefox and Thunderbird. Published on 2026-04-21, it carries a CVSS v3.1 base score of 9.8 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H) and is associated with CWE-288. The issue was addressed in Firefox version 150 and Thunderbird version 150.

The vulnerability enables exploitation by any unauthenticated remote attacker requiring low complexity and no user interaction. Successful attacks can result in high impacts to confidentiality, integrity, and availability, allowing attackers to bypass mitigations in cookie handling within the networking stack.

Mozilla's security advisories MFSA2026-30 and MFSA2026-33, along with Bugzilla entry 2023615, provide details on the flaw. Mitigation requires updating affected systems to Firefox 150 or Thunderbird 150.

Details

CWE(s)
CWE-288

Affected Products

mozilla
firefox
≤ 150.0
mozilla
thunderbird
≤ 150.0

MITRE ATT&CK Enterprise TechniquesAI

T1185 Browser Session Hijacking Collection
Adversaries may take advantage of security vulnerabilities and inherent functionality in browser software to change content, modify user-behaviors, and intercept information as part of various browser session hijacking techniques.
attack.mitre.org →
T1539 Steal Web Session Cookie Credential Access
An adversary may steal web application or service session cookies and use them to gain access to web applications or Internet services as an authenticated user without needing credentials.
attack.mitre.org →
Why these techniques?

Mitigation bypass in browser cookie handling directly enables/facilitates browser session hijacking and stealing web session cookies by circumventing security controls in the networking stack.

Confidence: MEDIUM · MITRE ATT&CK Enterprise v18.1

References