LiveActive security incident?Get immediate response
CVE Record

CVE-2026-4698: JIT miscompilation in the JavaScript Engine: JIT component

JIT miscompilation in the JavaScript Engine: JIT component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

HighCVSS 8.8Not KEV-listedUpdated
Discuss exposureBack to CVEs
Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

CVE-2026-4698 is a high-severity Mozilla JavaScript engine JIT compiler flaw fixed in Firefox and Thunderbird releases. A user must interact with malicious content, but the CVSS impact rates confidentiality, integrity, and availability as high. Organizations should prioritize browser and Thunderbird updates, especially on managed endpoints and Red Hat-packaged deployments.

Executive priority

Treat this as a near-term endpoint patching priority. It affects common user-facing software, has high potential impact, and requires user interaction rather than direct unauthenticated server compromise. No active exploitation evidence is provided, so urgency is high but not emergency-level from the supplied data.

Technical view

The issue is described as JIT miscompilation in the JavaScript Engine JIT component, associated with CWE-733 and CWE-843. CVSS 3.1 is 8.8: network reachable, low complexity, no privileges, user interaction required, unchanged scope, and high CIA impact. Mozilla lists fixed Firefox, Firefox ESR, Thunderbird, and Thunderbird ESR versions.

Likely exposure

Exposure is most likely on endpoints running unpatched Firefox, Firefox ESR, Thunderbird, or Thunderbird ESR, including enterprise Linux builds distributed through Red Hat advisories. The bundle does not provide precise vulnerable version ranges beyond fixed release information.

Exploitation context

The provided sources do not show CISA KEV listing or active exploitation evidence. CVSS indicates exploitation requires user interaction, likely through malicious web or content handling paths involving the JavaScript engine. No exploit steps or public weaponization details are included in the bundle.

Researcher notes

Key unknowns are exact vulnerable version ranges, exploitability details, and whether Thunderbird exposure differs by content handling configuration. Use Mozilla advisories and Bugzilla for canonical technical context, and Red Hat CSAF or errata for downstream package status.

Mitigation direction

  • Update Firefox to Mozilla fixed releases for the deployed release channel.
  • Update Thunderbird to Mozilla fixed releases for the deployed release channel.
  • Apply relevant Red Hat security advisories for packaged Mozilla products.
  • Check Mozilla and OS vendor guidance for exact affected-version mapping.
  • Prioritize managed endpoint rollout over ad hoc user self-updates.

Validation and detection

  • Inventory Firefox and Thunderbird versions across endpoints and servers.
  • Confirm Firefox 149, ESR 115.34, or ESR 140.9 where applicable.
  • Confirm Thunderbird 149 or Thunderbird 140.9 where applicable.
  • Verify Red Hat errata are applied on RHEL-derived systems.
  • Check vulnerability scanner findings against Mozilla and Red Hat advisories.
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-733: 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
cwe · low confidence lookup

CWE-843: 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-2026-4698 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
35Source 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-2026-4698Attack 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: JIT miscompilation in the JavaScript Engine: JIT component
other:Red Hat severity ratingcvssV3_1
  • 2026-03-24T13:01:51.367Z: Reported to Red Hat.
  • 2026-03-24T12:30:27.865Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
MozillaFirefox115.34, 140.9, 149Listed
MozillaThunderbird140.9, 149Listed
Weakness

CWE details

CWE-733CWE-843

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

CWE-733 · source CWE mapping

Compiler Optimization Removal or Modification of Security-critical Code

Compiler Optimization Removal or Modification of Security-critical Code represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs
CWE-843 · source CWE mapping

Access of Resource Using Incompatible Type ('Type Confusion')

Access of Resource Using Incompatible Type ('Type Confusion') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs