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CVE Record

CVE-2026-2764: JIT miscompilation, use-after-free in the JavaScript Engine: JIT component

JIT miscompilation, use-after-free in the JavaScript Engine: JIT component. This vulnerability was fixed in Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

CriticalCVSS 9.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysiscritical

Security readout for executives and security teams

Plain-English summary

CVE-2026-2764 is a critical Mozilla JavaScript engine flaw where JIT compilation can trigger use-after-free memory corruption. Mozilla states it was fixed in Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

Executive priority

Prioritize remediation in the next emergency browser and mail-client update cycle. The business risk is potential full confidentiality, integrity, and availability impact on exposed clients, with no active exploitation confirmed in the supplied evidence.

Technical view

The vulnerability is a JIT component miscompilation leading to CWE-416 use-after-free. The supplied CVSS 3.1 score is 9.8 with network, low-complexity, unauthenticated impact and high confidentiality, integrity, and availability impact. The source bundle does not describe exploit primitives or attack chains.

Likely exposure

Exposure is most likely on systems running Firefox or Thunderbird versions older than the fixed Mozilla releases, including environments receiving Mozilla packages through Linux vendor updates. The bundle does not identify other affected products.

Exploitation context

The bundle marks KEV as false and provides no cited evidence of active exploitation. Treat it as high-priority because it affects browser and mail-client JavaScript processing and carries critical CVSS impact, not because exploitation is confirmed.

Researcher notes

The useful public facts are limited: JIT miscompilation, use-after-free, Mozilla fixed releases, Red Hat advisory linkage, CVSS 9.8, and no KEV listing. Avoid assuming exploitability details, sandbox escape requirements, or mitigations beyond vendor updates.

Mitigation direction

  • Update Firefox to 148, ESR 115.33, ESR 140.8, or later applicable releases.
  • Update Thunderbird to 148, 140.8, or later applicable releases.
  • Apply relevant Red Hat errata where Mozilla packages are managed by Red Hat.
  • Check Mozilla and OS vendor advisories for environment-specific guidance.
  • Prioritize managed endpoints and shared workstations with browser or mail-client exposure.

Validation and detection

  • Inventory installed Firefox and Thunderbird versions across endpoints and servers.
  • Confirm versions meet or exceed the Mozilla fixed releases listed in advisories.
  • Check Linux package versions against applicable Red Hat errata or vendor advisories.
  • Verify vulnerability scanners map findings to CVE-2026-2764 and not only product family.
  • Track KEV and vendor advisories for any later exploitation status change.
Prepared
Confidence
medium
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-2026-2764 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
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
35Source 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-2026-2764Attack 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: JIT miscompilation, use-after-free in the JavaScript Engine: JIT component
other:Red Hat severity ratingcvssV3_1
  • 2026-02-24T14:04:49.869Z: Reported to Red Hat.
  • 2026-02-24T13:33:03.207Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
MozillaFirefox115.33, 140.8, 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.

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