External risk intelligence

macOS Tahoe Buffer Overflow Vulnerability

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2026-64691

The vulnerability affects macOS, a client-side operating system. While the reported issue relates to system processes, such vulnerabilities typically require local access or execution of specific applications on the endpoint rather than functioning as a public-facing network service or internet-accessible gateway.

Buffer Overflow

Apple Macos

26.0 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

This advisory concerns a critical vulnerability in macOS that could allow an application to cause unexpected system termination. While the technical details involve a buffer overflow, the executive-level implication is a potential disruption to system stability. The main concern is confirming relevance and exposure within your specific environment.

A system stability issue is present.
It could impact user experience and operations.
Assess your macOS exposure and impact.

Attack Path

How an attacker could exploit the issue

An attacker could exploit this vulnerability by sending specially crafted data to a vulnerable macOS system over the network. This could lead to an app causing an unexpected system termination. The specific entry conditions and exact triggering mechanisms beyond the mention of buffer overflow and improved size validation are not detailed in the provided information.

Network access is required.
A vulnerable app triggers the overflow.
Risk includes system termination.

Live Threat

Current exploitation, exposure, and threat context

This vulnerability could allow an app to cause unexpected system termination on macOS when supported by the advisory.

System termination.
Unexpected app execution.
Loss of unsaved work.

Operational Fix

Recommended remediation, mitigation, and detection steps

The primary responsibility for addressing this vulnerability likely lies with teams managing macOS endpoints, such as endpoint management or IT operations. The first critical step is to identify all macOS systems, assess their exposure to potential exploitation, and confirm business criticality. Once identified, the accountable owner for each affected asset should be determined to plan for remediation.

Asset owners should confirm system inventory.
Verify business criticality and exposure.
Plan coordinated maintenance for fixes.

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 macOS Tahoe?

macOS Tahoe is an operating system developed by Apple for Mac computers. It provides the core software environment that manages hardware resources, runs applications, and handles user interactions. This specific update addresses internal memory handling issues to ensure the system remains stable and responsive during standard operation.

What does CVE-2026-64691 mean by buffer overflow?

This vulnerability falls under the CWE-120 weakness class, which happens when a program writes more data to a memory buffer than it is designed to hold. In this case, the extra data spills into adjacent memory, causing the system to lose track of its tasks. This leads to an unexpected shutdown of the affected application or the system itself.

How can an attacker trigger this vulnerability?

An attacker would need to send specially crafted data to a vulnerable macOS system over a network. It is important to note that simply having a network connection is not enough; the bug specifically requires a vulnerable application to receive and process that malicious data to initiate the crash. Normal, benign network traffic will not trigger this issue.

Why does Halo Surface Signal rate this as very unlikely?

Halo Surface Signal assesses this as very unlikely because macOS is primarily a client-side operating system, not a public-facing network gateway. While the vulnerability exists, the need for specific conditions—such as a vulnerable app actively processing malicious data—makes it difficult for an attacker to reach this flaw from the open internet compared to traditional server services.

Do I need to take action for this macOS vulnerability?

Yes. Start by identifying which systems in your environment are running macOS Tahoe. Once you have a clear inventory, prioritize updates for systems that are mission-critical. Coordinate with your team to apply the official fix provided by Apple to ensure these systems are no longer susceptible to unexpected termination caused by this buffer overflow.

References

support.apple.com/en-us/128067

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.