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CVE Record

CVE-2026-8947: Use-after-free in the DOM: Bindings (WebIDL) component

Use-after-free in the DOM: Bindings (WebIDL) 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
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

CVE-2026-8947 is a high-severity Mozilla memory-safety flaw in Firefox and Thunderbird. A user would need to interact with malicious content, but successful exploitation could compromise confidentiality, integrity, and availability. Mozilla lists fixed releases for Firefox, Firefox ESR, and Thunderbird.

Executive priority

Prioritize remediation in the normal high-severity browser and email-client patch cycle. Escalate for high-risk users because exploitation could have full CIA impact, though active exploitation is not evidenced in the supplied sources.

Technical view

The issue is a use-after-free in DOM Bindings WebIDL, mapped to CWE-416 and CWE-825. CVSS 3.1 is 7.5 with network attack vector, no privileges required, user interaction required, high attack complexity, and high CIA impact. Mozilla says it is fixed in Firefox 151, ESR 115.36/140.11, Thunderbird 151, and Thunderbird 140.11.

Likely exposure

Exposure is likely where Firefox, Firefox ESR, or Thunderbird installations have not been updated to the fixed Mozilla releases. Red Hat advisories indicate downstream packaged products may also require vendor updates.

Exploitation context

The bundle does not show CISA KEV listing or cited evidence of active exploitation. The CVSS vector indicates remote delivery is possible, but exploitation requires user interaction and high attack complexity.

Researcher notes

Key gaps are exploitability details and Bugzilla contents, which may be restricted. Treat fixed-version wording carefully: the supplied description identifies those releases as fixed, not vulnerable. Avoid claiming exploitation without KEV or advisory evidence.

Mitigation direction

  • Update Firefox to 151 or applicable ESR fixed release listed by Mozilla.
  • Update Thunderbird to 151 or 140.11 where applicable.
  • Apply relevant Red Hat RHSA updates for downstream packaged builds.
  • Monitor Mozilla and Red Hat advisories for any additional vendor guidance.

Validation and detection

  • Inventory Firefox, Firefox ESR, and Thunderbird versions across managed endpoints.
  • Confirm installed versions meet or exceed the fixed releases named by Mozilla.
  • Check Red Hat package advisory status where Red Hat builds are used.
  • Document exceptions and assign owners for systems not yet updated.
Prepared
Confidence
high
Sources
10

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-416: 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.

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cwe · low confidence lookup

CWE-825: 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-2026-8947 mapping review

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

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.5 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/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
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:H/PR:N/UI:R/S:U/C:H/I:H/A:H1.65.9redhat-SADP
7.3CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L3.93.4CISA-ADP

Vulnerability scoring details

Base CVSS 3.1 score

7.5High
CVSS 3.1 vector shape for CVE-2026-8947Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/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: Use-after-free in the DOM: Bindings (WebIDL) component
other:Red Hat severity ratingcvssV3_1
  • 2026-05-19T14:03:11.971Z: Reported to Red Hat.
  • 2026-05-19T12:29:37.800Z: 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-416CWE-825

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