External risk intelligence

macOS Sandbox Breakout Vulnerability

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2026-64738

This vulnerability involves a sandbox breakout on macOS. Sandbox escapes require a malicious application to already be executing on the local system, making it a client-side, post-compromise, or local issue rather than an internet-facing service or remotely reachable network protocol.

Apple Macos

14.0 to before 14.8.815.0 to before 15.7.826.0 to before 26.6

Halo Surface Signal: 1 out of 5 — much less likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

A critical vulnerability has been identified in macOS that could allow a malicious application to bypass security restrictions and access unauthorized information or functionality. While the primary concern is confirming relevance and exposure within your environment, this type of issue warrants attention due to its potential to undermine system integrity.

App could escape its security sandbox.
Confirms relevance and exposure to affected systems.
Verify all systems are up-to-date and protected.

Attack Path

How an attacker could exploit the issue

Attackers could leverage a permissions flaw in macOS to escape a sandboxed environment. This could allow a malicious application, once installed on a device, to gain broader access to the system than it should have.

Malicious app must be installed.
Vulnerable permissions allow sandbox escape.
Sensitive data disclosure and modification.

Live Threat

Current exploitation, exposure, and threat context

A malicious application could break out of its sandbox on macOS. This could allow an attacker to gain broader access to system resources or user data beyond the application's intended permissions.

System data and user data may be exposed.
Malicious apps could break sandbox restrictions.
Potential for unauthorized access.

Operational Fix

Recommended remediation, mitigation, and detection steps

Real-world ownership for this vulnerability likely falls to teams managing macOS endpoints, such as IT infrastructure or endpoint security teams. The immediate practical step is to identify all macOS devices within the environment, confirm their current operating system versions, and assess business criticality and exposure. Once identified, responsible owners should be engaged to plan for the application of security updates during the next maintenance window, considering any dependencies or potential impacts.

Endpoint management teams own this issue.
Verify macOS versions and device criticality.
Plan and apply security updates.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

Halo Threat Intelligence helps prioritize remediation with Halo Surface Signal and H/A/L/O context. Start exposure validation with a free external attack surface trial.

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Frequently asked questions

What is the software affected by CVE-2026-64738?

This vulnerability affects macOS, the primary operating system used by Apple computers. It specifically impacts Sequoia 15.7.8, Sonoma 14.8.8, and Tahoe 26.6 versions. These systems use a sandbox mechanism to isolate applications, ensuring that software can only access its own files and designated resources rather than interacting with the broader operating system or other users' private data.

What does it mean to have a sandbox breakout vulnerability?

This issue is classified under CWE-284, which deals with improper access control. In plain terms, the macOS sandbox—a security boundary designed to keep applications contained—has a permissions flaw. This weakness allows a malicious application to bypass those restrictions, essentially 'breaking out' of its cage to access system resources or user information it is not authorized to reach.

How does an attacker trigger CVE-2026-64738?

To exploit this, a malicious application must already be installed and running on the target macOS device. The bug does not allow an attacker to remotely take over a system over the network from scratch. If an application is not installed on the system, or if it is running but lacks the specific malicious code to target this permissions flaw, the vulnerability remains untriggered.

Is my device at risk based on Halo Surface Signal?

Halo Surface Signal indicates that this vulnerability is very unlikely to be exploited as an internet-facing threat. Because it requires a malicious app to be executing locally on the device, it is considered a client-side, post-compromise issue. It is not an exposed network service that can be probed or attacked remotely by strangers across the internet.

When should I update my macOS devices for this issue?

You should prioritize updating to the latest macOS versions—Sequoia 15.7.8, Sonoma 14.8.8, or Tahoe 26.6—as part of your standard maintenance schedule. Since this is an endpoint-level issue, IT teams should verify which devices are running outdated versions and coordinate the deployment of these patches. Updating ensures that the sandbox restrictions are correctly enforced, preventing malicious apps from escaping their containers.

References

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.