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CVE Record

CVE-2026-2767: Use-after-free in the JavaScript: WebAssembly component

Use-after-free in the JavaScript: WebAssembly component. This vulnerability was fixed in Firefox 148, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

HighCVSS 8.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

CVE-2026-2767 is a high-severity Mozilla memory-safety flaw in the JavaScript WebAssembly component. A user would likely need to open malicious web or email content. Successful exploitation could compromise confidentiality, integrity, and availability. Mozilla states it is fixed in Firefox 148, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

Executive priority

Treat as a high-priority workstation and server-desktop patching item. It affects common user-facing software and has high impact if triggered, but current provided sources do not confirm active exploitation. Patch through normal emergency or accelerated browser update processes.

Technical view

The issue is a use-after-free vulnerability, CWE-416, in Mozilla’s JavaScript WebAssembly component. The CVSS 3.1 score is 8.8 with network attack vector, low complexity, no privileges required, and user interaction required. The source bundle names Firefox and Thunderbird and says the fix landed in Firefox 148, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

Likely exposure

Organizations are exposed where Mozilla Firefox or Thunderbird installations remain below the fixed releases identified by Mozilla, or where downstream vendor packages have not received the relevant security errata. Browser and email-client exposure is broad because users routinely process untrusted web and message content.

Exploitation context

The CVSS vector requires user interaction, so exploitation likely depends on convincing a user to open crafted web or email content. The provided sources do not show CISA KEV listing or confirmed active exploitation. Mozilla’s Bugzilla details may be restricted, so exploitability details are incomplete from public sources.

Researcher notes

Public data identifies the bug class and affected component but not root-cause detail. Bugzilla may have restricted information. Avoid assuming vulnerable version ranges beyond vendor advisories. Red Hat references indicate downstream tracking and errata; validate exact package impact against the applicable product channel.

Mitigation direction

  • Upgrade Firefox to 148 or Firefox ESR to 140.8 where applicable.
  • Upgrade Thunderbird to 148 or 140.8 where applicable.
  • Apply relevant Red Hat security errata for packaged Mozilla products.
  • Check Mozilla and OS vendor guidance for environment-specific remediation.
  • Prioritize managed endpoints that browse the internet or process external email.

Validation and detection

  • Inventory Firefox, Firefox ESR, and Thunderbird versions across endpoints.
  • Confirm installed versions meet or exceed Mozilla’s fixed releases.
  • Review Linux package status against relevant Red Hat advisories if applicable.
  • Check vulnerability scanner results for CVE-2026-2767 after updates.
  • Verify browser and mail-client auto-update policies are enabled and reporting.
Prepared
Confidence
high
Sources
9

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.

Open ATT&CK lookup
cve · low confidence lookup

CVE-2026-2767 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
8.8 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/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
34Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical 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
8.8CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H2.85.9CISA-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

8.8High
CVSS 3.1 vector shape for CVE-2026-2767Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/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 JavaScript: WebAssembly component
other:Red Hat severity ratingcvssV3_1
  • 2026-02-24T14:04:46.666Z: Reported to Red Hat.
  • 2026-02-24T13:33:05.551Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
MozillaFirefox140.8, 148Listed
MozillaThunderbird140.8, 148Listed
Weakness

CWE details

CWE-416

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