Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HCVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.
Summary
CVE-2026-6748 is a critical-severity Use of Uninitialized Variable (CWE-457) vulnerability in Mozilla Firefox. Its CVSS base score is 9.8 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique Junk Data (T1001.001); ranked at the 47th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SA-15 (Development Process, Standards, and Tools) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-6748 is an uninitialized memory vulnerability, classified under CWE-457, in the Audio/Video: Web Codecs component of Mozilla Firefox and Thunderbird. It affects versions of Firefox prior to 150, Firefox ESR prior to 140.10, Thunderbird prior to 150, and Thunderbird prior to 140.10. Published on 2026-04-21, the issue 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), marking it as critical severity due to its potential for severe impacts.
The vulnerability enables exploitation by a remote attacker over the network with low attack complexity, requiring no privileges, user interaction, or scope changes. Successful exploitation can result in high confidentiality, integrity, and availability impacts on the affected system.
Mozilla advisories MFSA2026-30, MFSA2026-32, MFSA2026-33, and MFSA2026-34 document the patch, confirming fixes in Firefox 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10. Additional technical details are available in Bugzilla entry 2022604. Security practitioners should prioritize updating to these versions to mitigate the risk.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-24089
Vulnerability Data
Uninitialized memory in the Audio/Video: Web Codecs component. This vulnerability was fixed in Firefox 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Developer testing and static analysis directly find uses of uninitialized variables before deployment.
Documented development standards and tools can enforce initialization requirements in code.
Engineering principles can mandate explicit variable initialization to avoid uninitialized use.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Secure SDLC practices directly catch uninitialized-variable defects via static analysis and code review while the control encompasses many additional development controls.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.