LiveActive security incident?Get immediate response
CVE Record

CVE-2026-8946: Incorrect boundary conditions in the Audio/Video: Web Codecs component

Incorrect boundary conditions in the Audio/Video: Web Codecs component. This vulnerability was fixed in Firefox 151, Firefox ESR 115.36, Firefox ESR 140.11, Thunderbird 151, and Thunderbird 140.11.

HighCVSS 7.5Not KEV-listedUpdated
Discuss exposureBack to CVEs
Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

CVE-2026-8946 is a high-severity Mozilla Web Codecs boundary-condition flaw fixed in Firefox, Firefox ESR, and Thunderbird releases. The public data indicates possible exposure of sensitive information, not system takeover. Treat it as an urgent browser and mail-client update issue, especially where managed desktops or Red Hat packages lag behind.

Executive priority

Prioritize remediation this patch cycle or sooner for managed browsers and mail clients. The issue is high severity with sensitive-data impact, but the provided evidence does not show active exploitation, so this is urgent hygiene rather than a confirmed incident response trigger.

Technical view

The issue is described as incorrect boundary conditions in Mozilla's Audio/Video Web Codecs component, mapped to CWE-119 and CWE-787. CVSS 3.1 is 7.5 with network attack vector, low complexity, no privileges, no user interaction, unchanged scope, and high confidentiality impact. Mozilla lists fixed versions; Red Hat published downstream advisories.

Likely exposure

Exposure is most likely on endpoints or servers running affected Mozilla Firefox, Firefox ESR, or Thunderbird builds, including downstream Red Hat-packaged versions. The exact vulnerable version ranges are not fully detailed in the provided bundle; verify installed versions against Mozilla and Red Hat advisories.

Exploitation context

The bundle does not show CISA KEV listing or cite active exploitation. The CVSS vector indicates remote, low-complexity exploitation without privileges or user interaction, but public evidence provided here does not establish weaponized attacks or exploitation in the wild.

Researcher notes

Public details are limited to component, weakness class, CVSS, fixed releases, and vendor advisories. Avoid assuming code execution or specific media parsing triggers from the supplied data. The affected range needs confirmation from Mozilla advisory text and downstream package metadata.

Mitigation direction

  • Update Firefox to Mozilla's fixed release for the installed channel.
  • Update Firefox ESR to 115.36 or 140.11 where applicable.
  • Update Thunderbird to 151 or 140.11 where applicable.
  • Apply relevant Red Hat security errata for packaged Mozilla components.
  • Check vendor guidance for any environment-specific mitigations.

Validation and detection

  • Inventory Firefox, Firefox ESR, and Thunderbird versions across managed endpoints.
  • Confirm installed builds meet or exceed Mozilla's fixed versions.
  • For Red Hat systems, verify applicable RHSA packages are installed.
  • Review vulnerability scanner findings for CVE-2026-8946 after updates.
  • Track exceptions where legacy ESR channels remain deployed.
Prepared
Confidence
medium
Sources
11

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-119: 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-787: 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-2026-8946 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
High
CVSS
7.5 (3.1)
Known Exploited
No
Published

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

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
31Source links

SSVC decision data

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

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
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N3.93.6CISA-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

7.5High
CVSS 3.1 vector shape for CVE-2026-8946Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

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

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: Incorrect boundary conditions in the Audio/Video: Web Codecs component
other:Red Hat severity ratingcvssV3_1
  • 2026-05-19T14:01:55.843Z: Reported to Red Hat.
  • 2026-05-19T12:29:36.254Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
MozillaFirefox115.36, 140.11, 151Listed
MozillaThunderbird140.11, 151Listed
Weakness

CWE details

CWE-119CWE-787

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

CWE-119 · source CWE mapping

Improper Restriction of Operations within the Bounds of a Memory Buffer

Improper Restriction of Operations within the Bounds of a Memory Buffer represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs
CWE-787 · source CWE mapping

Out-of-bounds Write

Out-of-bounds Write represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs