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Mozilla Firefox CVE-2026-16356

| EUVDEUVD-2026-46204 CRITICAL
Use After Free (CWE-416)
2026-07-21 mozilla GHSA-97hw-vmr9-c44j
Information Disclosure Use After Free Memory Corruption Red Hat Mozilla
9.8
CVSS 3.1 · Vendor: mozilla
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Severity by source

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

Sandbox escape presupposes chaining a content-process compromise (AC:H) and requires the user to load malicious content (UI:R); crossing the sandbox boundary is a scope change (S:C) with full host impact.

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
7.5 HIGH
qualitative

Primary rating from Vendor (mozilla).

CVSS VectorVendor: mozilla

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

Lifecycle Timeline

4
Analysis Generated
Jul 22, 2026 - 17:12 vuln.today
CVSS changed
Jul 22, 2026 - 16:22 NVD
9.8 (CRITICAL)
CVE Published
Jul 21, 2026 - 12:37 cve.org
UNKNOWN (no severity yet)
CVE Published
Jul 21, 2026 - 12:37 cve.org
CRITICAL 9.8

DescriptionCVE.org

Sandbox escape due to use-after-free in the Disability Access APIs component. This vulnerability was fixed in Firefox 153, Firefox ESR 115.38, and Firefox ESR 140.13.

AnalysisAI

Sandbox escape via use-after-free in Mozilla Firefox's Disability Access (accessibility) APIs allows an attacker who has compromised the content process to break out of the browser sandbox and gain code execution at the host privilege level. It affects Firefox before 153 and the ESR 115.x and 140.x branches, was reported and patched by Mozilla, and carries no public exploit at time of analysis. EPSS is low (0.15%, 5th percentile) and it is not on CISA KEV, indicating no observed exploitation.

Technical ContextAI

The flaw is a CWE-416 use-after-free in Firefox's accessibility subsystem (the 'Disability Access APIs' that expose the DOM/UI tree to assistive technologies such as screen readers via platform interfaces like MSAA/IAccessible2 or ATK). A use-after-free occurs when the code continues to reference memory that has already been freed, allowing an attacker who controls heap allocation to place attacker-chosen data at the reused location and hijack control flow. Because the accessibility bridge straddles the boundary between the sandboxed content process and higher-privileged browser components, corrupting it enables a sandbox escape rather than only in-content memory corruption. The single affected CPE is cpe:2.3:a:mozilla:firefox, and Mozilla's own tags classify it as memory corruption / use-after-free with potential information disclosure.

RemediationAI

Vendor-released patch: upgrade to Firefox 153, Firefox ESR 115.38, or Firefox ESR 140.13 depending on your channel - this is the primary and complete fix per Mozilla advisories MFSA2026-68/69/70. Because Firefox auto-updates by default, ensure managed or air-gapped deployments that pin versions or disable updates are manually rolled forward, and verify enterprise policy (policies.json/GPO) is not holding back the update. As an interim compensating control on unpatched hosts, exploitation depends on the accessibility layer, so disabling the accessibility service (set accessibility.force_disabled to 1 in about:config or via enterprise policy) reduces the attack surface of the Disability Access APIs - with the significant trade-off that this breaks screen readers and other assistive technology and must not be applied to users who rely on them. Given the sandbox-escape nature, maintaining OS-level exploit mitigations and least-privilege for the browser process further limits post-escape impact. No workaround substitutes for updating.

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Same weakness CWE-416 – Use After Free

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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-2026-16356 vulnerability details – vuln.today
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