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Mozilla Firefox CVE-2026-74954

| EUVDEUVD-2026-60681 HIGH
Observable Discrepancy (CWE-203)
2026-08-18 mozilla GHSA-8c9h-mhqx-6q3f
Information Disclosure Mozilla Red Hat Suse
7.5
CVSS 3.1 · Vendor: mozilla
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Severity by source

Vendor (mozilla) PRIMARY
7.5 HIGH
AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
vuln.today AI
5.3 MEDIUM

AC:H reflects that reliable cache timing side-channels require controlled conditions; UI:R because victim must navigate to attacker content.

3.1 AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N
4.0 AV:N/AC:H/AT:N/PR:N/UI:A/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
SUSE
HIGH
qualitative
Red Hat
6.1 MEDIUM
qualitative

Primary rating from Vendor (mozilla).

CVSS VectorVendor: mozilla

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

Lifecycle Timeline

3
Analysis Generated
Aug 18, 2026 - 20:26 vuln.today
CVE Published
Aug 18, 2026 - 12:23 cve.org
HIGH 7.5
CVE Published
Aug 18, 2026 - 12:23 cve.org
UNKNOWN (no severity yet)

DescriptionCVE.org

Information disclosure due to side-channel in the Storage: Cache API component. This vulnerability was fixed in Firefox 154 and Firefox ESR 153.1.

AnalysisAI

Side-channel information disclosure in Firefox's Storage: Cache API (CWE-203) allows remote unauthenticated attackers to infer sensitive cached data through observable timing discrepancies between cache hits and misses. All Firefox versions prior to 154 and Firefox ESR versions prior to 153.1 are affected per Mozilla advisories mfsa2026-74 through mfsa2026-80. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access
Victim loads attacker-controlled web page
Delivery
JavaScript probes Storage Cache API with timing requests
Exploit
Measure cache-hit vs cache-miss timing discrepancies
Execution
Infer cross-origin cached resource URLs
Impact
Reconstruct sensitive browsing activity or session state
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Vulnerability AssessmentAI

Exploitation The Storage: Cache API is a standard browser feature enabled by default in Firefox - no non-default configuration is required. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The official CVSS 3.1 score of 7.5 (AV:N/AC:L/PR:N/UI:N) reflects high theoretical severity, but several signals moderate the real-world urgency: side-channel attacks against browser cache APIs (CWE-203) are technically non-trivial - they require precise timing measurements under controlled network conditions, suggesting AC:L may overstate ease of exploitation. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario An attacker hosts a malicious web page containing JavaScript that systematically queries the Storage: Cache API with timing measurements, probing whether resources from other origins have been cached in the victim's browser. By loading the page in an unpatched Firefox instance, the attacker's script observes timing discrepancies between cache hits and misses, enabling inference of which URLs the victim has recently accessed or which web applications are active in their session. …
Remediation Upgrade to Mozilla Firefox 154 or Firefox ESR 153.1, both confirmed as fixed versions per the CVE description and Mozilla advisories (https://www.mozilla.org/security/advisories/mfsa2026-74/ and https://www.mozilla.org/security/advisories/mfsa2026-77/). … Detailed patch versions, workarounds, and compensating controls in full report.
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Recommended ActionAI

Within 24 hours: Conduct inventory of Firefox versions and deployment scope across high-value asset categories (development teams, financial systems, cloud administration). …

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Same weakness CWE-203 – Observable Discrepancy

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Same technique Information Disclosure

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Vendor StatusVendor

SUSE

Severity: Important
Product Status
Container suse/kiosk/firefox-esr:140.14-75.12 Affected
SUSE Linux Enterprise Desktop 15 SP7 SUSE Linux Enterprise High Performance Computing 15 SP7 SUSE Linux Enterprise Module for Desktop Applications 15 SP7 SUSE Linux Enterprise Server 15 SP7 SUSE Linux Enterprise Server for SAP Applications 15 SP7 Fixed
SUSE Linux Enterprise High Performance Computing 15 SP4-ESPOS Fixed
SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS Fixed
SUSE Linux Enterprise High Performance Computing 15 SP5-ESPOS Fixed

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CVE-2026-74954 vulnerability details – vuln.today
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