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Firefox CVE-2026-6751

| EUVDEUVD-2026-24092 HIGH
Use of Uninitialized Variable (CWE-457)
2026-04-21 mozilla GHSA-mwvh-c89q-73j6
Information Disclosure Mozilla
7.3
CVSS 3.1 · Vendor: mozilla
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Severity by source

Vendor (mozilla) PRIMARY
7.3 HIGH
AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
SUSE
HIGH
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:L/I:L/A:L
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
Low
Availability
Low

Lifecycle Timeline

8
Patch released
Apr 29, 2026 - 02:30 nvd
Patch available
Analysis Updated
Apr 22, 2026 - 00:41 vuln.today
v2 (cvss_changed)
Re-analysis Queued
Apr 22, 2026 - 00:22 vuln.today
cvss_changed
Analysis Generated
Apr 21, 2026 - 20:24 vuln.today
CVSS changed
Apr 21, 2026 - 20:22 NVD
7.3 (None) 7.3 (HIGH)
EUVD ID Assigned
Apr 21, 2026 - 13:15 euvd
EUVD-2026-24092
Analysis Generated
Apr 21, 2026 - 13:15 vuln.today
CVE Published
Apr 21, 2026 - 12:40 nvd
HIGH 7.3

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 attackers to disclose sensitive data, modify limited application state, and potentially trigger denial of service without authentication. The vulnerability affects Firefox versions prior to 150 and Firefox ESR versions prior to 140.10. Mozilla has released patches addressing this memory safety issue. EPSS data not available, but SSVC framework indicates non-automated exploitation with partial technical impact. No public exploit identified at time of analysis.

Technical ContextAI

This vulnerability stems from CWE-457 (Use of Uninitialized Variable) within Firefox's Audio/Video Web Codecs component, a modern web API that provides low-level access to media encoders and decoders. The Web Codecs API allows JavaScript to directly manipulate video frames and audio data for tasks like video editing, streaming, and conferencing. When memory is allocated but not properly initialized before use, it retains previous data from other operations. An attacker-controlled web page could trigger codec operations that read this uninitialized memory, potentially exposing remnants of other browsing data, cryptographic material, or application state. The CVSS vector indicates network-accessible exploitation with low complexity, affecting confidentiality, integrity, and availability within the browser's sandbox (S:U). The CPE identifies Mozilla Firefox as the affected product across all platforms where Firefox runs.

RemediationAI

Upgrade to Firefox version 150 or later for standard release channel users, or Firefox ESR version 140.10 or later for extended support users. Mozilla has addressed this uninitialized memory issue in security advisories MFSA2026-30, MFSA2026-32, MFSA2026-33, and MFSA2026-34 available at mozilla.org/security/advisories/. If immediate patching is not feasible, organizations can disable the Web Codecs API by setting the preference 'media.webcodecs.enabled' to false in about:config or via enterprise policy deployment, though this will break web applications relying on this API for video conferencing, streaming, or media editing functionality. Content Security Policy headers can also restrict script execution from untrusted origins, reducing exposure to malicious sites attempting to trigger the vulnerability, but this provides only partial protection as users may navigate to attacker-controlled domains directly.

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Same weakness CWE-457 – Use of Uninitialized Variable

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Vendor StatusVendor

SUSE

Severity: High
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-2026-6751 vulnerability details – vuln.today
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