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CVE Record

CVE-2026-6748: Uninitialized memory in the Audio/Video: Web Codecs component

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.

CriticalCVSS 9.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysiscritical

Security readout for executives and security teams

Plain-English summary

CVE-2026-6748 is a critical Mozilla Web Codecs memory bug affecting Firefox and Thunderbird. Mozilla says it is fixed in Firefox 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10. Because the flaw scores 9.8, organizations should treat outdated installations as urgent exposure, especially on managed desktops and Linux distributions.

Executive priority

Patch on an urgent cycle. This is a critical memory-safety vulnerability in widely deployed client software, with official fixes available and potential impact across confidentiality, integrity, and availability.

Technical view

The issue is uninitialized memory in Mozilla's Audio/Video Web Codecs component, mapped to CWE-457 and CWE-824. The CVSS 3.1 vector is network reachable, low complexity, no privileges, no user interaction, unchanged scope, and high confidentiality, integrity, and availability impact. Public source details do not describe exploit mechanics.

Likely exposure

Exposure is likely where Firefox, Firefox ESR, or Thunderbird remain below Mozilla's fixed releases, or where downstream packages have not received Red Hat or vendor errata updates. Exact vulnerable version ranges are not fully stated in the supplied bundle.

Exploitation context

The bundle does not show CISA KEV listing, and no cited source states active exploitation. Treat this as high-risk due to critical severity and browser/mail-client attack surface, but do not claim exploitation is occurring from the supplied evidence.

Researcher notes

Evidence supports a Web Codecs uninitialized-memory issue with high CVSS impact, but the provided public bundle lacks exploit details, vulnerable range precision, and proof of active exploitation. Avoid assumptions beyond Mozilla and Red Hat advisories.

Mitigation direction

  • Update Firefox to version 150 or Firefox ESR 140.10 or later.
  • Update Thunderbird to version 150 or 140.10 or later.
  • Apply relevant Red Hat security advisories for packaged Mozilla components.
  • Prioritize managed desktop, server GUI, VDI, and mail-client fleets.
  • Check Mozilla and distribution advisories for environment-specific guidance.

Validation and detection

  • Inventory installed Firefox, Firefox ESR, and Thunderbird versions across endpoints.
  • Confirm versions meet or exceed Mozilla's fixed releases.
  • Check Linux package status against referenced Red Hat errata.
  • Verify vulnerability scanner findings map to CVE-2026-6748.
  • Document exceptions where affected products are absent or already updated.
Prepared
Confidence
high
Sources
12

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · low confidence lookup

CWE-457: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

Open ATT&CK lookup
cwe · low confidence lookup

CWE-824: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

Open ATT&CK lookup
cve · low confidence lookup

CVE-2026-6748 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

Open ATT&CK lookup
Vulnerability profileCVE Program record
Severity
Critical
CVSS
9.8 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

2CVSS vectors
5Timeline events
2ADP providers
36Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: yesTechnical Impact: total

CVSS vector scores

2 official scores

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
9.8CVSS 3.1CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H3.95.9CISA-ADP
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H1.65.9redhat-SADP

Vulnerability scoring details

Base CVSS 3.1 score

9.8Critical
CVSS 3.1 vector shape for CVE-2026-6748Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. ADP timelineredhat-SADP

    Made public.

  3. CVE publishedCVE Program

    The CVE record was published.

  4. ADP timelineredhat-SADP

    Reported to Red Hat.

  5. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
cvssV3_1other:ssvc
redhat-SADPfirefox: thunderbird: Uninitialized memory in the Audio/Video: Web Codecs component
other:Red Hat severity ratingcvssV3_1
  • 2026-04-21T14:02:39.417Z: Reported to Red Hat.
  • 2026-04-21T12:40:45.923Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
MozillaFirefox140.10, 150Listed
MozillaThunderbird140.10, 150Listed
Weakness

CWE details

CWE-457CWE-824

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-457 · source CWE mapping

Use of Uninitialized Variable

Use of Uninitialized Variable represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs
CWE-824 · source CWE mapping

Access of Uninitialized Pointer

Access of Uninitialized Pointer represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs