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CVE Record

CVE-2026-8389: JIT miscompilation in the JavaScript Engine: JIT component

JIT miscompilation in the JavaScript Engine: JIT component. This vulnerability was fixed in Firefox 150.0.3.

HighCVSS 8.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

CVE-2026-8389 is a high-severity Firefox JavaScript engine JIT miscompilation issue. A user likely needs to visit or open attacker-controlled web content. Successful exploitation could affect confidentiality, integrity, and availability. Mozilla states it was fixed in Firefox 150.0.3.

Executive priority

Treat as urgent browser patching, especially for user endpoints that access the public internet. The risk is high, but the provided evidence does not prove active exploitation.

Technical view

The vulnerability is described as JIT miscompilation in Firefox’s JavaScript Engine JIT component. The CVSS 3.1 score is 8.8 with network attack vector, low complexity, no privileges, and required user interaction. The source bundle does not clearly enumerate vulnerable prior versions beyond stating the fix release.

Likely exposure

Organizations with Firefox deployed on user workstations or managed Linux desktops may be exposed if browsers are not updated to the fixed release. Exposure depends on actual installed Firefox versions and distro package status.

Exploitation context

CISA KEV is false in the bundle, so active exploitation is not established. The bundle includes a public GitHub reference tagged as exploit, but its contents and reliability are not validated here.

Researcher notes

Key uncertainty is version scope: the bundle says the vulnerability was fixed in Firefox 150.0.3 but does not list vulnerable prior releases. Avoid assuming exploitability details from the GitHub reference without independent review.

Mitigation direction

  • Update Firefox to 150.0.3 or the vendor-supported fixed package.
  • Check Mozilla advisory MFSA2026-45 for definitive vendor guidance.
  • Check Red Hat guidance for affected enterprise Linux packages.
  • Prioritize browser updates on internet-facing user endpoints.
  • Limit risky browsing until affected systems are updated.

Validation and detection

  • Inventory Firefox versions across endpoints and servers with desktop packages.
  • Confirm installed builds are Firefox 150.0.3 or vendor-fixed equivalents.
  • Review Red Hat CSAF/VEX data for product applicability.
  • Verify endpoint management reports successful browser update deployment.
  • Monitor Mozilla and Red Hat advisories for revisions.
Prepared
Confidence
medium
Sources
8

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-119: 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-686: 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-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-2026-8389 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
7Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: pocAutomatable: 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-2026-8389Attack 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: JIT miscompilation in the JavaScript Engine: JIT component
other:Red Hat severity ratingcvssV3_1
  • 2026-05-12T14:01:13.009Z: Reported to Red Hat.
  • 2026-05-12T12:36:12.516Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
MozillaFirefox150.0.3Listed
Weakness

CWE details

CWE-119CWE-686CWE-733CWE-843

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