Cyber Resilience

CVE-2026-6778

Medium

Published: 21 April 2026

Published
21 April 2026
Modified
22 April 2026
KEV Added
—
Patch
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CVSS Score v3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
EPSS Score 0.0026 17.0th percentile
Risk Priority 35 floored blend · peak EPSS

Summary

CVE-2026-6778 is a medium-severity NULL Pointer Dereference (CWE-476) vulnerability in Mozilla Firefox. Its CVSS base score is 5.3 (Medium).

Operationally, exploitation aligns with the MITRE ATT&CK technique Application or System Exploitation (T1499.004); ranked at the 17.0th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified are NIST 800-53 SI-2 (Flaw Remediation) and SC-39 (Process Isolation).

Deeper analysis

CVE-2026-6778 is an invalid pointer vulnerability (CWE-476, CWE-824) in the Audio/Video: Playback component of Mozilla Firefox and Thunderbird. Published on 2026-04-21, it carries a CVSS v3.1 base score of 5.3 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L). The issue was addressed in Firefox 150 and Thunderbird 150.

Unauthenticated remote attackers can exploit this vulnerability over the network with low attack complexity and without requiring user interaction or privileges. Successful exploitation results in a low-impact denial of service, such as application crashes affecting availability.

Mozilla's security advisories MFSA2026-30 and MFSA2026-33 provide details on the vulnerability and patches, recommending upgrades to Firefox 150 or Thunderbird 150. Further technical information is available in Bugzilla ticket 2022746.

OWASP Top 10 for Web (2025)

A10:2025 Mishandling of Exceptional Conditions

EU & UK References

Vulnerability details

Invalid pointer in the Audio/Video: Playback component. This vulnerability was fixed in Firefox 150 and Thunderbird 150.

CWE(s)
CWE-476CWE-824

Related Threats

MITRE ATT&CK Enterprise TechniquesAI

T1499.004 Application or System Exploitation Impact
Adversaries may exploit software vulnerabilities that can cause an application or system to crash and deny availability to users.
attack.mitre.org →
Why these techniques?

Invalid pointer dereference in browser media playback directly enables application crash via exploitation, matching T1499.004 Endpoint Denial of Service (Application or System Exploitation).

Confidence: HIGH · MITRE ATT&CK Enterprise v19.0

CVEs Like This One

CVE-2026-6755Same product: Mozilla Firefox
CVE-2026-6781Same product: Mozilla Firefox
CVE-2026-6754Same product: Mozilla Firefox
CVE-2026-2801Same product: Mozilla Firefox
CVE-2026-6773Same product: Mozilla Firefox
CVE-2026-6758Same product: Mozilla Firefox
CVE-2026-6747Same product: Mozilla Firefox
CVE-2026-0889Same product: Mozilla Firefox
CVE-2025-9182Same product: Mozilla Firefox
CVE-2026-6759Same product: Mozilla Firefox

Affected Assets

mozilla
firefox
≤ 150.0
mozilla
thunderbird
≤ 150.0

Mitigating Controls

Mitigating Controls (NIST 800-53 r5) AI

SI-2 Flaw Remediation good match
prevent

Directly requires timely application of vendor patches to remediate the invalid-pointer flaw fixed in Firefox/Thunderbird 150.

SI-16 Memory Protection partial match
prevent

Employs memory-protection techniques that can mitigate exploitation of invalid pointers (CWE-476/824) in the media playback component.

SC-39 Process Isolation partial match
prevent

Process isolation limits the blast radius of an application crash caused by the pointer dereference to the affected browser/tab only.

References