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Mozilla Firefox CVE-2026-16391

| EUVDEUVD-2026-46228 HIGH
Information Exposure (CWE-200)
2026-07-21 mozilla GHSA-jvcf-79h8-93pm
Information Disclosure Red Hat Mozilla
High
Disputed · 7.5 Vendor: mozilla
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Severity by source

Sources disagree (Medium–Critical)
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
6.5 MEDIUM

Network-delivered via web content with no auth, but realistic exploitation requires the victim to load a malicious page (UI:R); impact is confidentiality-only.

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

vuln.today treats the vendor’s rating as authoritative. A higher third-party CVSS (e.g. CISA-ADP) is shown for transparency but does not drive the headline severity.

CVSS VectorVendor: mozilla

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

Lifecycle Timeline

4
Analysis Generated
Jul 22, 2026 - 19:04 vuln.today
CVSS changed
Jul 22, 2026 - 18:22 NVD
7.5 (HIGH)
CVE Published
Jul 21, 2026 - 12:38 cve.org
UNKNOWN (no severity yet)
CVE Published
Jul 21, 2026 - 12:38 cve.org
HIGH 7.5

DescriptionCVE.org

Information disclosure in the Storage: IndexedDB component. This vulnerability was fixed in Firefox 153 and Firefox ESR 140.13.

AnalysisAI

Information disclosure in Mozilla Firefox's Storage: IndexedDB component allows a remote attacker to leak sensitive data across origins or from other browsing contexts without authentication or user interaction. The flaw affects Firefox releases prior to 153 and ESR builds prior to 140.13; there is no public exploit identified at time of analysis, and its EPSS score (0.15%, 5th percentile) indicates low near-term exploitation likelihood despite a CVSS of 7.5. Mozilla has released fixed builds, so the practical priority is prompt browser updating rather than emergency response.

Technical ContextAI

IndexedDB is the browser's transactional client-side database API that lets web pages persist structured data keyed by origin, and it is a security-sensitive boundary because it stores per-site data that must remain isolated between origins. This issue is classified CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor), meaning the root cause is a logic or isolation defect in how the IndexedDB storage layer partitions or returns data, permitting information that should be confined to one context to be read by an unauthorized one. The affected component is the Gecko-based Firefox engine (CPE cpe:2.3:a:mozilla:firefox), so any content-rendering surface that can invoke IndexedDB - a visited web page or embedded content - exercises the vulnerable code path.

RemediationAI

Vendor-released patch: upgrade to Firefox 153 or later on the standard release channel, or to Firefox ESR 140.13 or later on the extended support channel, as documented in Mozilla advisories mfsa2026-68 (https://www.mozilla.org/security/advisories/mfsa2026-68/) and mfsa2026-70 (https://www.mozilla.org/security/advisories/mfsa2026-70/). Because the fix ships in a full browser build, applying the update is the complete remediation and no partial configuration change fully closes the issue. If updating cannot be completed immediately, the practical compensating control is to limit exposure to untrusted web content - for example restricting high-risk browsing or enforcing managed-update policies so endpoints receive 153/140.13 promptly - noting these controls reduce but do not eliminate exposure and impose usability trade-offs; disabling IndexedDB is not a supported user-facing toggle and would break many legitimate sites.

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Same weakness CWE-200 – Information Exposure

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Same technique Information Disclosure

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Vendor StatusVendor

SUSE

Severity: Critical
Product Status
SUSE Linux Enterprise High Performance Computing 15 SP4-ESPOS Affected
SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS Affected
SUSE Linux Enterprise High Performance Computing 15 SP5-ESPOS Affected
SUSE Linux Enterprise High Performance Computing 15 SP5-LTSS Affected
SUSE Linux Enterprise Module for Desktop Applications 15 SP7 Affected

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CVE-2026-16391 vulnerability details – vuln.today
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