CVE-2026-64738 Overview
CVE-2026-64738 is a permissions vulnerability in Apple macOS that allows a malicious application to break out of its sandbox. Apple addressed the issue by applying additional restrictions in macOS Sequoia 15.7.8, macOS Sonoma 14.8.8, and macOS Tahoe 26.6. The flaw is categorized under [CWE-284] (Improper Access Control) and affects the operating system's sandbox enforcement mechanism.
A successful sandbox escape lets an application access resources and interfaces that should remain isolated from untrusted code. This undermines a core macOS defense boundary that constrains what applications can read, write, or execute.
Critical Impact
A malicious app running under the macOS sandbox can escape its container and reach resources outside the intended isolation boundary, breaking a foundational macOS security control.
Affected Products
- Apple macOS Sequoia versions prior to 15.7.8
- Apple macOS Sonoma versions prior to 14.8.8
- Apple macOS Tahoe versions prior to 26.6
Discovery Timeline
- 2026-07-27 - CVE-2026-64738 published to the National Vulnerability Database (NVD)
- 2026-07-30 - Last updated in NVD database
Technical Details for CVE-2026-64738
Vulnerability Analysis
The vulnerability resides in the macOS sandbox permission model. The sandbox enforces mandatory access controls that restrict what an application process can do at runtime. Apple's advisory describes the fix as adding restrictions to a permissions check, indicating that the prior implementation allowed an action that should have been denied.
When exploited, a malicious app can perform operations outside the boundaries defined by its sandbox profile. This can include accessing files, IPC endpoints, or system services normally reserved for higher-privileged or unsandboxed contexts. The result is a lateral expansion of the app's effective permissions on the host.
Root Cause
The root cause is an improper access control condition ([CWE-284]) in the sandbox permissions logic. A code path evaluated a request without applying all required constraints, so an operation that should have been rejected was allowed. Apple's remediation added those missing restrictions to close the gap.
Attack Vector
Exploitation requires a malicious or compromised application to run on the target macOS system. Once loaded, the app invokes the affected code path to gain access to resources outside its sandbox. Delivery mechanisms include drive-by downloads, trojanized applications distributed outside the App Store, and supply chain compromise of legitimate software.
Apple has not published technical exploitation details. Refer to the Apple Support Document #128072 for vendor guidance. There are no public proof-of-concept exploits and the issue is not listed in the CISA Known Exploited Vulnerabilities catalog at this time.
Detection Methods for CVE-2026-64738
Indicators of Compromise
- Sandboxed applications spawning child processes or accessing file paths outside their container directory under ~/Library/Containers/<bundle-id>/
- Unexpected xpc or Mach IPC connections initiated by App Store or third-party sandboxed applications
- Applications reading or writing to protected locations such as ~/Library/Application Support/, ~/Documents/, or system directories without a corresponding user prompt
Detection Strategies
- Correlate process lineage telemetry with sandbox profile expectations to flag sandboxed apps performing out-of-profile file or network operations
- Monitor macOS Endpoint Security Framework (ESF) events, in particular ES_EVENT_TYPE_NOTIFY_OPEN and ES_EVENT_TYPE_NOTIFY_EXEC, for anomalous access patterns from sandboxed binaries
- Alert on installations of applications signed with recently issued developer IDs that immediately request or attempt broad filesystem access
Monitoring Recommendations
- Track macOS build versions across the fleet to identify hosts running versions prior to 15.7.8, 14.8.8, or 26.6
- Baseline expected behavior for common sandboxed applications and alert on deviations such as new outbound network destinations or IPC targets
- Ingest Unified Log entries related to com.apple.sandbox denials and successes into a centralized SIEM for retrospective hunting
How to Mitigate CVE-2026-64738
Immediate Actions Required
- Update all Apple macOS endpoints to macOS Sequoia 15.7.8, macOS Sonoma 14.8.8, or macOS Tahoe 26.6
- Prioritize systems that run third-party or unsigned applications, developer workstations, and shared multi-user Macs
- Restrict installation of applications from outside the App Store using MDM policies until patching is complete
Patch Information
Apple released fixes in macOS Sequoia 15.7.8, macOS Sonoma 14.8.8, and macOS Tahoe 26.6. Vendor advisories are available at Apple Support Document #128067, Apple Support Document #128071, and Apple Support Document #128072. Deploy updates through Apple Software Update or your MDM solution.
Workarounds
- No official workaround exists; patching is the required remediation
- Reduce exposure by enforcing Gatekeeper and Notarization policies to block unsigned or unnotarized applications
- Apply the principle of least privilege by limiting user accounts to standard (non-administrator) roles where feasible
# Verify current macOS build on an endpoint
sw_vers
# Trigger a software update check via CLI
sudo softwareupdate --list
sudo softwareupdate --install --all --restart
# Confirm Gatekeeper is enabled
spctl --status
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
