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CVE Record

CVE-2026-8388: Incorrect boundary conditions in the JavaScript Engine: JIT component

Incorrect boundary conditions in the JavaScript Engine: JIT component. This vulnerability was fixed in Firefox 150.0.3, Firefox ESR 115.36, Firefox ESR 140.11, and Thunderbird 140.11.

HighCVSS 7.5Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

CVE-2026-8388 is a high-severity Mozilla JavaScript engine JIT flaw fixed in Firefox, Firefox ESR, and Thunderbird releases. A victim must interact with attacker-controlled content, but successful exploitation could affect confidentiality, integrity, and availability. Treat outdated browsers and mail clients as priority patch targets.

Executive priority

Prioritize remediation on user workstations and any systems that process web or email content. This is not confirmed exploited in the supplied evidence, but the potential impact is broad and browser/mail client exposure is common.

Technical view

The issue is described as incorrect boundary conditions in the JavaScript Engine JIT component, mapped to CWE-119 and CWE-787. The CVSS 3.1 vector is network, high complexity, no privileges, user interaction required, unchanged scope, with high C/I/A impact. Fixed versions are Firefox 150.0.3, Firefox ESR 115.36/140.11, and Thunderbird 140.11.

Likely exposure

Exposure is most likely on endpoints running Mozilla Firefox, Firefox ESR, or Thunderbird that have not applied the named fixed releases. Red Hat advisories indicate downstream package handling may also matter for Linux fleets. Exact vulnerable version ranges should be confirmed from Mozilla and distribution advisories.

Exploitation context

The source bundle does not show CISA KEV listing or any cited evidence of active exploitation. The CVSS vector indicates remote reachability with required user interaction and high attack complexity. Do not assume exploitation in the wild without additional vendor or KEV evidence.

Researcher notes

Public details are limited in the supplied bundle. Focus assessment on version validation, JIT exposure through JavaScript-capable content, downstream vendor package status, and whether Mozilla Bugzilla or advisories later disclose exploitation or additional technical constraints.

Mitigation direction

  • Upgrade Firefox to 150.0.3 or later where applicable.
  • Upgrade Firefox ESR to 115.36 or 140.11 or later.
  • Upgrade Thunderbird to 140.11 or later where applicable.
  • Apply relevant Red Hat security errata for managed Linux packages.
  • Check Mozilla and distribution guidance for exact supported release channels.

Validation and detection

  • Inventory Firefox, Firefox ESR, and Thunderbird versions across endpoints.
  • Confirm installed versions meet or exceed the fixed releases.
  • Review Red Hat errata applicability for RHEL-managed packages.
  • Verify patch deployment through endpoint management or package reporting.
  • Check whether unsupported release channels remain in use.
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-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-787: 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-2026-8388 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
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
30Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: yesTechnical 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
6.5CVSS 3.1MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N3.92.5CISA-ADP

Vulnerability scoring details

Base CVSS 3.1 score

7.5High
CVSS 3.1 vector shape for CVE-2026-8388Attack 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: Incorrect boundary conditions in the JavaScript Engine: JIT component
other:Red Hat severity ratingcvssV3_1
  • 2026-05-12T14:01:26.546Z: Reported to Red Hat.
  • 2026-05-12T12:36:10.633Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
MozillaFirefox115.36, 140.11, 150.0.3Listed
MozillaThunderbird140.11Listed
Weakness

CWE details

CWE-119CWE-787

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