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Mozilla Firefox CVE-2026-74981

| EUVDEUVD-2026-60694 HIGH
Origin Validation Error (CWE-346)
2026-08-18 mozilla GHSA-37q5-qg7q-c8f4
Information Disclosure Mozilla
High
Disputed · 8.1 Vendor: mozilla
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Severity by source

Sources disagree (Low–High)
Vendor (mozilla) PRIMARY
8.1 HIGH
AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
vuln.today AI
8.1 HIGH

Network-delivered via malicious webpage (AV:N, AC:L), no attacker privileges (PR:N), victim must visit page (UI:R); cross-origin read and write possible (C:H/I:H), no process escape or availability impact (S:U, A:N).

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

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

Lifecycle Timeline

4
Analysis Generated
Aug 20, 2026 - 18:29 vuln.today
CVSS changed
Aug 20, 2026 - 18:22 NVD
8.1 (HIGH)
CVE Published
Aug 18, 2026 - 12:23 cve.org
HIGH 8.1
CVE Published
Aug 18, 2026 - 12:23 cve.org
UNKNOWN (no severity yet)

DescriptionCVE.org

Site isolation issue in the Audio/Video: Web Codecs component. This vulnerability was fixed in Firefox 154 and Firefox ESR 153.1.

AnalysisAI

Site isolation bypass in Mozilla Firefox's Audio/Video Web Codecs component allows remote attackers to perform cross-origin data access, potentially reading or modifying content belonging to other origins within the browser. Rooted in CWE-346 (Origin Validation Error), the flaw affects all Firefox releases prior to 154 and all ESR releases prior to 153.1. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access
Victim visits attacker-controlled webpage
Delivery
Malicious page delivers crafted Web Codecs media
Exploit
Firefox Web Codecs component processes media without proper origin validation
Execution
Cross-origin data boundary bypassed
Persist
Attacker reads or modifies content from other origins
Impact
Sensitive data (tokens, cookies, DOM) exfiltrated
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Vulnerability AssessmentAI

Exploitation The victim must be running Mozilla Firefox below version 154 or Firefox ESR below version 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:H/I:H/A:N) scores 8.1, reflecting low attack complexity, no attacker privileges, and high confidentiality and integrity impact - consistent with a browser-side site isolation bypass exploitable from any network-accessible malicious page. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario An attacker hosts a webpage containing a crafted audio or video stream processed by the Firefox Web Codecs API. When a user on an unpatched Firefox version visits the page, the malicious codec content exploits the origin validation failure to read session tokens, authentication cookies, or sensitive DOM content from other origins open in the same browser session. …
Remediation Upgrade to Firefox 154 (standard release channel) or Firefox ESR 153.1 (extended support release channel), as confirmed by Mozilla's security advisories at 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, inventory Firefox deployments with emphasis on systems accessing sensitive customer data, financial platforms, or internal applications. …

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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-2026-74981 vulnerability details – vuln.today
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