Site isolation issue in the CSS Parsing and Computation component (CVE-2026-74986) | HOL Guard CVE

Unknown severity · Source severity not reportedCVE-2026-74986

Site isolation issue in the CSS Parsing and Computation component

Answer in brief

CVE-2026-74986 records a Unknown severity vulnerability in Site isolation issue in the CSS Parsing and Computation 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 Aug 18, 2026Updated Aug 18, 2026Source checked Aug 18, 2026First seen by HOL Aug 18, 2026Material review Aug 18, 2026

Upstream Advisory

Key facts

Risk: Unknown severitySource severity not reported
Exploitation: Not marked as known exploited
Affected software: Not mapped
Fix availability: Not reported

Why this deserves its current priority

A CVSS score is not reported in the current record. 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
Aug 18, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Aug 18, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Aug 18, 2026

Sources and claim methodology

Upstream source description

Site isolation issue in the CSS Parsing and Computation component. This vulnerability was fixed in Firefox 154 and Firefox ESR 153.1.

Quoted source text, attributed separately from HOL analysis.

Back to active CVEs

Unknown severity · Source severity not reportedCVE-2026-74986

Site isolation issue in the CSS Parsing and Computation component

Answer in brief

Analysis pending evidence review

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

Published Aug 18, 2026Updated Aug 18, 2026Source checked Aug 18, 2026First seen by HOL Aug 18, 2026Material review Aug 18, 2026

Upstream Advisory

Key facts

Risk: Unknown severitySource severity not reported
Exploitation: Not marked as known exploited
Affected software: Not mapped
Fix availability: Not reported

Why this deserves its current priority

A CVSS score is not reported in the current record. 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
Aug 18, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Aug 18, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Aug 18, 2026

Sources and claim methodology

Upstream source description

Site isolation issue in the CSS Parsing and Computation component. This vulnerability was fixed in Firefox 154 and Firefox ESR 153.1.

Quoted source text, attributed separately from HOL analysis.