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CVE Record

CVE-2026-12299: JIT miscompilation in the DOM: Core & HTML component

JIT miscompilation in the DOM: Core & HTML component. This vulnerability was fixed in Firefox 152, Firefox ESR 140.12, Firefox ESR 115.37, Thunderbird 152, and Thunderbird 140.12.

HighCVSS 7.5Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

A Mozilla browser and mail client bug could cause Firefox or Thunderbird to handle content incorrectly after a JIT compiler mistake in DOM code. Exploitation requires user interaction and is rated high because successful abuse could affect confidentiality, integrity, and availability. Mozilla lists fixed Firefox, ESR, and Thunderbird releases.

Executive priority

Treat this as a high-priority client software update, especially for managed desktops and servers where Firefox or Thunderbird are installed. The issue needs user interaction, but the potential impact is broad enough to justify prompt patching through normal emergency browser-update processes.

Technical view

CVE-2026-12299 is a JIT miscompilation issue in Mozilla's DOM: Core & HTML component, mapped to CWE-733 and CWE-843. CVSS 3.1 is 7.5: network reachable, high complexity, no privileges, user interaction required, unchanged scope, and high confidentiality, integrity, and availability impact.

Likely exposure

Exposure is most likely on endpoints running Firefox, Firefox ESR, or Thunderbird versions older than Mozilla's fixed releases: Firefox 152, ESR 140.12, ESR 115.37, Thunderbird 152, or Thunderbird 140.12. Red Hat advisories indicate downstream package relevance for affected Red Hat environments.

Exploitation context

The source bundle does not show CISA KEV listing or other cited evidence of active exploitation. The CVSS vector indicates exploitation is remote but requires user interaction and high attack complexity. Do not assume reliable public exploitation without additional vendor or threat-intelligence evidence.

Researcher notes

Available evidence identifies the vulnerable area and fixed releases but does not provide public exploit details in the bundle. Focus validation on version detection, vendor advisory mapping, and downstream package errata. Avoid assuming exploitability beyond the CVSS vector and Mozilla's high-severity classification.

Mitigation direction

  • Update Firefox to Mozilla's fixed release or later.
  • Update Firefox ESR to 140.12, 115.37, or later as applicable.
  • Update Thunderbird to 152, 140.12, or later as applicable.
  • Apply relevant Red Hat security errata for packaged Mozilla products.
  • Check Mozilla and OS vendor advisories for environment-specific guidance.

Validation and detection

  • Inventory Firefox, Firefox ESR, and Thunderbird versions across endpoints.
  • Confirm deployed versions meet or exceed Mozilla's fixed releases.
  • Review Red Hat package status where Mozilla products are OS-managed.
  • Track Mozilla advisories MFSA2026-57 through MFSA2026-61 for product-specific coverage.
  • Verify patch deployment through endpoint management or vulnerability scanner results.
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.

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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-2026-12299 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
7.5 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:H/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
31Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

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
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
5.4CVSS 3.1MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N2.82.5CISA-ADP

Vulnerability scoring details

Base CVSS 3.1 score

7.5High
CVSS 3.1 vector shape for CVE-2026-12299Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:H/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 DOM: Core & HTML component
other:Red Hat severity ratingcvssV3_1
  • 2026-06-16T14:01:13.587Z: Reported to Red Hat.
  • 2026-06-16T11:52:32.885Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
MozillaFirefox115.37, 140.12, 152Listed
MozillaThunderbird140.12, 152Listed
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