Critical · CVSS 9.8CVE-2026-2766

Use-after-free in the JavaScript Engine: JIT component

Answer in brief

CVE-2026-2766 records a Critical severity (CVSS 9.8) vulnerability in Use-after-free in the JavaScript Engine: JIT component. The current sources do not mark it as known exploited. Affected software not mapped in the current feed; confirm the named product and version against your inventory.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Feb 24, 2026Updated Jul 15, 2026Source checked Aug 5, 2026First seen by HOL Jul 15, 2026Material review Jul 15, 2026

Upstream Advisory

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Critical · CVSS 9.8CVE-2026-2766

Use-after-free in the JavaScript Engine: JIT component

Answer in brief

CVE-2026-2766 records a Critical severity (CVSS 9.8) vulnerability in Use-after-free in the JavaScript Engine: JIT component. The current sources do not mark it as known exploited. Affected software not mapped in the current feed; confirm the named product and version against your inventory.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Feb 24, 2026Updated Jul 15, 2026Source checked Aug 5, 2026First seen by HOL Jul 15, 2026Material review Jul 15, 2026

Upstream Advisory

Key facts

Risk: Critical · CVSS 9.8
Exploitation: Not marked as known exploited
Affected software: Not mapped
Fix availability: Not reported

Why this deserves its current priority

CVSS is 9.8. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

Affected software not mapped in the current feed; confirm the named product and version against your inventory.

Recommended response

Confirm exposure. Identify whether the named product or interface exists in your inventory, then review the linked upstream references for affected versions and vendor guidance.

Evidence timeline and material changes

Published upstream
Feb 24, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Jul 15, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Jul 15, 2026

Sources and claim methodology

Upstream source description

Use-after-free in the JavaScript Engine: JIT component. This vulnerability was fixed in Firefox 148, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

Quoted source text, attributed separately from HOL analysis.

Key facts

Risk: Critical · CVSS 9.8
Exploitation: Not marked as known exploited
Affected software: Not mapped
Fix availability: Not reported

Why this deserves its current priority

CVSS is 9.8. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

Affected software not mapped in the current feed; confirm the named product and version against your inventory.

Recommended response

Confirm exposure. Identify whether the named product or interface exists in your inventory, then review the linked upstream references for affected versions and vendor guidance.

Evidence timeline and material changes

Published upstream
Feb 24, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Jul 15, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Jul 15, 2026

Sources and claim methodology

Upstream source description

Use-after-free in the JavaScript Engine: JIT component. This vulnerability was fixed in Firefox 148, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

Quoted source text, attributed separately from HOL analysis.