CVE-2026-64691 Overview
CVE-2026-64691 is a buffer overflow vulnerability in Apple macOS resolved through improved size validation. Apple addressed the flaw in macOS Tahoe 26.6. A malicious application can trigger the condition and cause unexpected system termination, leading to denial of service on affected hosts.
The issue is tracked as CWE-120, classic buffer copy without checking size of input. Apple published the fix in its security advisory referenced below.
Critical Impact
A local application can exploit the buffer overflow to terminate the operating system, disrupting availability on unpatched macOS installations.
Affected Products
- Apple macOS versions prior to macOS Tahoe 26.6
- Systems running unpatched macOS builds identified in the Apple advisory
- Endpoints and workstations where untrusted applications may execute
Discovery Timeline
- 2026-07-27 - CVE-2026-64691 published to the National Vulnerability Database
- 2026-07-28 - Last updated in NVD database
Technical Details for CVE-2026-64691
Vulnerability Analysis
The vulnerability is a buffer overflow in a macOS component that fails to validate input size before copying data into a fixed-length buffer. Apple's advisory states the condition allows an application to cause unexpected system termination. The result is a loss of availability on the affected system.
Buffer overflows of this class occur when the destination buffer size is not enforced during a copy operation. Adjacent memory structures, control data, or kernel state can be corrupted depending on where the overflow occurs. Apple's remediation involved adding size checks around the affected copy paths.
The advisory does not disclose the specific component, function, or code path affected. See the Apple Support Article for the vendor's technical description.
Root Cause
The root cause is missing size validation before writing attacker-influenced data into a bounded buffer. This maps to [CWE-120]. Apple's fix adds explicit bounds checking to reject or truncate oversized inputs.
Attack Vector
An application running on the affected macOS system supplies crafted input that reaches the vulnerable code path. The overflow corrupts memory and triggers system termination. Exploitation requires code execution as an app on the host, meaning delivery typically occurs through a malicious or trojanized application.
No public proof-of-concept exploit is available at the time of publication. The vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog.
Detection Methods for CVE-2026-64691
Indicators of Compromise
- Unexpected kernel panics or system restarts on macOS hosts running versions prior to macOS Tahoe 26.6
- Crash reports in /Library/Logs/DiagnosticReports/ referencing memory corruption in system components
- Recently installed or executed untrusted applications preceding system termination events
Detection Strategies
- Correlate application execution telemetry with system crash events to identify suspicious causation patterns
- Monitor for applications performing unusual system-call sequences that touch the affected macOS subsystems
- Track macOS build versions across the fleet to identify hosts still exposed to the flaw
Monitoring Recommendations
- Ingest macOS unified logs and DiagnosticReports into a centralized log platform for crash pattern analysis
- Alert on repeated unexpected reboots on the same endpoint within short time windows
- Baseline application inventory to detect newly introduced binaries preceding stability incidents
How to Mitigate CVE-2026-64691
Immediate Actions Required
- Update all affected macOS endpoints to macOS Tahoe 26.6 or later
- Inventory macOS build versions across managed devices and prioritize unpatched hosts
- Restrict installation of untrusted or unsigned applications through MDM policy
Patch Information
Apple resolved CVE-2026-64691 in macOS Tahoe 26.6 by adding improved size validation. Refer to the Apple Support Article for the official advisory and update instructions.
Workarounds
- Enforce Gatekeeper and notarization requirements to block unsigned applications
- Limit local user privileges to reduce the population of applications that can be installed and executed
- Apply application allowlisting through MDM to prevent execution of unvetted binaries until patching completes
# Verify installed macOS version
sw_vers -productVersion
# Trigger a software update check on macOS
sudo softwareupdate --list
sudo softwareupdate --install --all --restart
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
