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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 memory safety flaw in Mozilla’s JavaScript WebAssembly component. A user would need to interact with attacker-controlled content. Successful exploitation could compromise confidentiality, integrity, and availability. Mozilla says it is fixed in Firefox 148, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

Executive priority

Prioritize patching in the normal high-severity endpoint browser and mail-client cycle. Escalate faster for high-risk users, unmanaged endpoints, or environments with delayed browser updates. No active exploitation is evidenced in the supplied sources.

Technical view

The issue is a CWE-416 use-after-free in the JavaScript WebAssembly component. The CVSS 3.1 score is 8.8 with network attack vector, low complexity, no privileges required, user interaction required, unchanged scope, and high CIA impact. Public source details do not include exploit mechanics.

Likely exposure

Organizations are exposed where Firefox, Firefox ESR, or Thunderbird remain below the Mozilla fixed releases, including Linux distributions that ship Mozilla packages. Exposure is most relevant on endpoints where users browse or open untrusted content.

Exploitation context

The bundle does not show CISA KEV listing or cited evidence of active exploitation. The risk remains material because the flaw is remotely reachable through user interaction and affects a memory-unsafe browser component with high impact ratings.

Researcher notes

Public evidence identifies class, component, CVSS, fixed versions, and vendor advisories, but not technical root cause or proof-of-concept details. Avoid assuming exploitability beyond the CVSS attributes. Red Hat VEX and errata indicate downstream package handling should be checked separately.

Mitigation direction

  • Upgrade Firefox to 148 or later where applicable.
  • Upgrade Firefox ESR to 140.8 or later.
  • Upgrade Thunderbird to 148 or 140.8 or later, as applicable.
  • Apply relevant Red Hat security errata for managed Linux packages.
  • Check Mozilla and OS vendor guidance for environment-specific instructions.

Validation and detection

  • Inventory Firefox, Firefox ESR, and Thunderbird versions across endpoints.
  • Confirm fixed versions are installed after patch deployment.
  • Check Red Hat package advisory status where Red Hat builds are used.
  • Review vulnerability scanner results for CVE-2026-2767 detection.
  • Verify no unsupported Mozilla package channels remain in production.
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-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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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.

Open ATT&CK lookup
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.

CWE-416 · source CWE mapping

Use After Free

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

Open CWE intelligenceSame-CWE CVEs