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Mozilla Firefox CVE-2026-74963

| EUVDEUVD-2026-60661 MEDIUM
Origin Validation Error (CWE-346)
2026-08-18 mozilla GHSA-8r32-h7pp-v9x9
Authentication Bypass Mozilla Red Hat Suse
5.4
CVSS 3.1 · Vendor: mozilla
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Severity by source

Vendor (mozilla) PRIMARY
5.4 MEDIUM
AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N
vuln.today AI
5.4 MEDIUM

Network vector, no privileges needed, but user must visit attacker page; cookie-level leak yields only low C/I impact with no availability consequence.

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

Primary rating from Vendor (mozilla).

CVSS VectorVendor: mozilla

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

Lifecycle Timeline

3
Analysis Generated
Aug 18, 2026 - 20:44 vuln.today
CVE Published
Aug 18, 2026 - 12:23 cve.org
MEDIUM 5.4
CVE Published
Aug 18, 2026 - 12:23 cve.org
UNKNOWN (no severity yet)

DescriptionCVE.org

Same-origin policy bypass in the Networking: Cookies component. This vulnerability was fixed in Firefox 154, Firefox ESR 140.14, and Firefox ESR 153.1.

AnalysisAI

Same-origin policy bypass in Firefox's Networking: Cookies component exposes users to cross-origin cookie theft and manipulation when visiting attacker-controlled pages. All Firefox versions prior to 154 and both ESR branches prior to ESR 140.14 and ESR 153.1 are affected, with Mozilla publishing at least six separate security advisories (mfsa2026-74 through mfsa2026-80) indicating broad coverage across release tracks. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access
Attacker crafts malicious web page exploiting SOP bypass
Delivery
Victim clicks phishing link or visits attacker page in unpatched Firefox
Exploit
Page script triggers origin validation flaw in Networking: Cookies component
Execution
Script reads or modifies cookies from a distinct trusted origin
Persist
Attacker receives exfiltrated session cookie
Impact
Attacker replays cookie to hijack authenticated session
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Vulnerability AssessmentAI

Exploitation The victim must be running an unpatched version of Mozilla Firefox - specifically, standard release versions prior to 154, ESR 140.x versions prior to 140.14, or ESR 153.x versions prior to 153.1. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The CVSS 3.1 vector AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N yields a 5.4 Medium score, which is well-calibrated for this class of vulnerability. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario An attacker registers a domain and hosts a page containing JavaScript that triggers Firefox's flawed cookie origin validation, allowing the script to read session cookies scoped to a separate trusted origin the victim is authenticated to. The attacker delivers the link via phishing email or malvertising, and when the victim clicks it in a vulnerable Firefox version, the attacker's script exfiltrates the victim's session cookie for a banking or enterprise SSO portal, enabling session hijacking without credentials. …
Remediation The primary remediation is to upgrade to a patched Firefox release: standard-channel users should update to Firefox 154 or later; organizations on the ESR 140.x track should update to Firefox ESR 140.14 or later; organizations on the ESR 153.x track should update to Firefox ESR 153.1 or later. … Detailed patch versions, workarounds, and compensating controls in full report.
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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-2026-74963 vulnerability details – vuln.today
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