What is the CVSS score of CVE-2026-8953?

CVE-2026-8953 has a contested CVSS base score of 9.6 from a third party (e.g. CISA-ADP), while the vendor rates it Critical. vuln.today uses the vendor rating as authoritative.

Which versions of Mozilla Firefox are affected by CVE-2026-8953?

Mozilla Firefox (versions before 151, ESR before 115.36/140.11) contains a critical sandbox-escape vulnerability (CVE-2026-8953, CVSS 9.6) that allows complete system compromise through malicious…. A patch is available.

How to fix or mitigate CVE-2026-8953?

Within 24 hours, identify all Firefox installations organization-wide and issue an urgent patch directive to IT teams and end users. Within 7 days, deploy patches to Firefox version 151 or later for standard releases, Firefox ESR 115.36 or later for ESR 115 branch deployments, and Firefox ESR 140.11 or later for ESR 140 branch deployments, with priority to systems used for sensitive work or external communications. Within 30 days, verify 100% patch deployment through endpoint management tools and close any remediation tickets for non-compliant systems.

Mozilla Firefox CVE-2026-8953

EUVD-2026-30901 CRITICAL

Use After Free (CWE-416)

2026-05-19 mozilla

GHSA-c3qv-mh67-fpxw

Information Disclosure Use After Free Memory Corruption Mozilla

Critical

Disputed · 9.6 NVD

Severity by source

Sources disagree (Medium–Critical)

NVD PRIMARY

9.6 CRITICAL

AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H

vuln.today AI

8.3 HIGH

Remote, unauthenticated, user-visits-page (UI:R) with sandbox-escape scope change and total impact; AC raised to H because reliable UAF exploitation needs heap grooming.

3.1 AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:H

4.0 AV:N/AC:H/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H

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 VectorNVD

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

Required

Scope

Changed

Confidentiality

High

Integrity

High

Availability

High

Lifecycle Timeline

Analysis Generated

Jul 23, 2026 - 17:44 vuln.today

CVE Published

May 19, 2026 - 12:29 nvd

UNKNOWN (no severity yet)

CVE Published

May 19, 2026 - 12:29 cve.org

CRITICAL 9.6

DescriptionCVE.org

Sandbox escape due to use-after-free in the Disability Access APIs component. This vulnerability was fixed in Firefox 151, Firefox ESR 115.36, and Firefox ESR 140.11.

AnalysisAI

Sandbox escape in Mozilla Firefox via a use-after-free (CWE-416) in the Disability Access (accessibility) APIs lets a remote attacker who lures a user to malicious web content break out of the content sandbox and gain total control over confidentiality, integrity, and availability. The flaw affects Firefox before 151, Firefox ESR before 115.36, and Firefox ESR before 140.11, and is fixed in those releases. No public exploit identified at time of analysis and EPSS is very low (0.04%), but the CVSS 9.6 rating and scope-changing sandbox escape make it a high-severity patch priority.

Technical ContextAI

The vulnerability lives in Firefox's Disability Access APIs - the accessibility layer that exposes the browser's UI and rendered content to assistive technologies such as screen readers via platform accessibility interfaces. The root cause is CWE-416 (use-after-free): an object in the accessibility subsystem is freed while a dangling reference remains reachable, so subsequent reuse of that memory can corrupt the heap. Because the accessibility code bridges the sandboxed content process and higher-privilege browser/OS components, a successful UAF here is leveraged as a sandbox escape rather than a mere content-process crash. The single affected CPE is cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*, and the tags (Use After Free, Memory Corruption, Information Disclosure) confirm the memory-safety class.

RemediationAI

Vendor-released patch: upgrade to Firefox 151, Firefox ESR 115.36, or Firefox ESR 140.11 as appropriate for your channel - this is the primary and complete fix. On enterprise Linux, apply the corresponding distribution updates (e.g., SUSE SUSE-SU-2026:2039 at https://www.suse.com/support/update/SUSE-SU-2026:2039/, and equivalent Red Hat errata) via your package manager and restart the browser so the patched libraries load. Reference the Mozilla advisories (https://www.mozilla.org/security/advisories/mfsa2026-46/ through mfsa2026-51/) for exact per-channel build numbers. If immediate patching is not possible, reduce exposure by keeping users on the managed ESR channel and avoiding untrusted sites; because the flaw is in the accessibility layer, environments that do not require assistive technology can consider disabling accessibility support (Firefox preference accessibility.force_disabled=1 or equivalent enterprise policy) as a partial compensating control, with the trade-off that screen readers and other assistive tools stop working - this narrows but does not guarantee elimination of the attack surface, so patching remains required.

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Vendor StatusVendor

SUSE

Severity: Critical

Product	Status
SUSE Linux Enterprise Server 12 SP5-LTSS	Fixed
SUSE Linux Enterprise Server LTSS Extended Security 12 SP5	Fixed
openSUSE Tumbleweed	Fixed
SUSE Linux Enterprise High Performance Computing 15 SP4-ESPOS	Affected
SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS	Affected

CVE-2026-8953 vulnerability details – vuln.today

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Mozilla Firefox CVE-2026-8953

Severity by source

CVSS VectorNVD

Lifecycle Timeline

DescriptionCVE.org

AnalysisAI

Technical ContextAI

RemediationAI

More in Mozilla

Same weakness CWE-416 – Use After Free

Same technique Information Disclosure

Vendor StatusVendor

SUSE

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External POC / Exploit Code