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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

A critical Mozilla JavaScript engine flaw can lead to memory corruption through a use-after-free condition in JIT code. Mozilla says it is fixed in newer Firefox and Thunderbird releases. The business risk is highest where browsers or email clients remain unpatched across user endpoints.

Executive priority

Patch urgently through normal emergency endpoint update channels. This is a critical memory-safety issue in widely used user-facing software, but current sources do not show confirmed active exploitation.

Technical view

CVE-2026-2764 is a CWE-416 use-after-free tied to JIT miscompilation in Mozilla’s JavaScript Engine JIT component. The supplied CVSS v3.1 score is 9.8 with network, low-complexity, no-privilege impact and high confidentiality, integrity, and availability impact. Fixed releases are listed for Firefox, Firefox ESR, Thunderbird, and Thunderbird ESR.

Likely exposure

Exposure is likely on endpoints running Mozilla Firefox or Thunderbird below the fixed releases: Firefox 148, Firefox ESR 115.33 or 140.8, Thunderbird 148, or Thunderbird 140.8. The bundle does not provide exact vulnerable version ranges beyond those fixed-version statements.

Exploitation context

The source bundle marks CISA KEV as false and provides no cited evidence of active exploitation. Treat exploitation status as unconfirmed, not actively exploited. The critical CVSS score and browser JavaScript engine location still warrant rapid patch validation.

Researcher notes

Focus validation on version and package provenance, not exploit reproduction. Bugzilla details may be restricted or incomplete. Red Hat VEX and RHSA references indicate downstream tracking, but the supplied bundle does not establish all affected downstream package versions.

Mitigation direction

  • Upgrade Firefox to 148 or supported ESR fixed releases.
  • Upgrade Thunderbird to 148 or Thunderbird 140.8.
  • Apply relevant Red Hat security advisories where Mozilla packages are distributed by Red Hat.
  • Check Mozilla and OS vendor guidance for package-specific fixed builds.
  • Prioritize managed endpoints that process web pages or HTML email content.

Validation and detection

  • Inventory Firefox and Thunderbird versions across desktops and servers.
  • Compare installed versions against Mozilla’s listed fixed releases.
  • Check Linux package advisories for relevant Red Hat RHSA updates.
  • Confirm no business-critical hosts remain on unfixed ESR builds.
  • Document any exceptions and monitor vendor advisories for updates.
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-2026-2764 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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