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Firefox CVE-2026-6748

| EUVDEUVD-2026-24089 CRITICAL
Use of Uninitialized Variable (CWE-457)
2026-04-21 mozilla GHSA-75xc-fv5m-pprr
Information Disclosure Mozilla
9.8
CVSS 3.1 · Vendor: mozilla
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Severity by source

Vendor (mozilla) PRIMARY
9.8 CRITICAL
AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
SUSE
CRITICAL
qualitative
Red Hat
7.5 HIGH
qualitative

Primary rating from Vendor (mozilla).

CVSS VectorVendor: mozilla

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

Lifecycle Timeline

8
Patch released
Apr 29, 2026 - 02:30 nvd
Patch available
Analysis Updated
Apr 22, 2026 - 00:29 vuln.today
v2 (cvss_changed)
Re-analysis Queued
Apr 22, 2026 - 00:22 vuln.today
cvss_changed
Analysis Generated
Apr 21, 2026 - 19:22 vuln.today
CVSS changed
Apr 21, 2026 - 19:22 NVD
9.8 (CRITICAL)
EUVD ID Assigned
Apr 21, 2026 - 13:15 euvd
EUVD-2026-24089
Analysis Generated
Apr 21, 2026 - 13:15 vuln.today
CVE Published
Apr 21, 2026 - 12:40 nvd
CRITICAL 9.8

DescriptionCVE.org

Uninitialized memory in the Audio/Video: Web Codecs component. This vulnerability was fixed in Firefox 150 and Firefox ESR 140.10.

AnalysisAI

Uninitialized memory access in Firefox's Web Codecs API enables remote code execution without authentication. Attackers can exploit this CWE-457 (Use of Uninitialized Variable) flaw through network-accessible vectors with low complexity (AV:N/AC:L/PR:N/UI:N) to achieve complete system compromise including data exfiltration, arbitrary code execution, and denial of service. CVSS 9.8 severity is supported by SSVC assessment indicating automatable exploitation with total technical impact. Vendor-released patches available in Firefox 150 and Firefox ESR 140.10. CISA SSVC reports no active exploitation at time of analysis, though the vulnerability is classified as automatable with total technical impact.

Technical ContextAI

This vulnerability affects Mozilla Firefox's implementation of the Web Codecs API, a modern browser interface for encoding and decoding audio and video streams. The flaw stems from CWE-457 (Use of Uninitialized Variable), where memory allocated for audio/video processing operations is accessed before being properly initialized. In memory-unsafe languages like C/C++ commonly used in browser media components, uninitialized memory can contain residual data from previous operations or random values. When this memory is used in calculations, buffer operations, or control flow decisions, it creates undefined behavior that attackers can manipulate. The CPE identifier cpe:2.3:a:mozilla:firefox confirms both standard Firefox and Extended Support Release (ESR) channels are affected. The Web Codecs API processes untrusted media data from web content, making it an attractive attack surface for remote exploitation through malicious websites or multimedia content.

RemediationAI

Upgrade immediately to Firefox 150 or later for standard channel users, or Firefox ESR 140.10 or later for Extended Support Release users. Mozilla Security Advisories MFSA2026-30 (https://www.mozilla.org/security/advisories/mfsa2026-30/) and MFSA2026-32 (https://www.mozilla.org/security/advisories/mfsa2026-32/) contain complete upgrade instructions and release notes. For environments unable to patch immediately, implement compensating controls by disabling JavaScript-accessible media features through Firefox enterprise policies: set 'media.webcodecs.enabled' to false in about:config or via Group Policy Object, which prevents web content from accessing the vulnerable Web Codecs API. Note this workaround breaks legitimate functionality on sites using modern video conferencing, media editing, or streaming features. Network-level controls such as deploying web filtering to block known-malicious media exploitation sites provide additional defense-in-depth but cannot prevent zero-day exploitation attempts. Organizations managing Firefox at scale should prioritize ESR channel deployments for more predictable patching cycles while maintaining rapid update capabilities for critical vulnerabilities like this.

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Vendor StatusVendor

SUSE

Severity: Critical
Product Status
SUSE Liberty Linux 10 Fixed
SUSE Liberty Linux 8 Fixed
SUSE Liberty Linux 9 Fixed
SUSE Linux Enterprise Server 16.0 SUSE Linux Enterprise Server for SAP applications 16.0 Fixed
openSUSE Leap 16.0 Fixed

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CVE-2026-6748 vulnerability details – vuln.today
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