CVE-2026-20667 Overview
CVE-2026-20667 is a sandbox escape vulnerability affecting multiple Apple operating systems. The flaw stems from a logic issue that Apple addressed through improved checks. An app running on an affected device may be able to break out of its sandbox, bypassing the isolation boundary that separates third-party applications from sensitive system resources and other apps. The vulnerability is classified under [CWE-693] Protection Mechanism Failure. Apple resolved the issue across iOS, iPadOS, macOS Sequoia, macOS Sonoma, macOS Tahoe, and watchOS in coordinated security updates.
Critical Impact
A malicious or compromised app can escape the Apple sandbox to access protected resources, leading to high confidentiality, integrity, and availability impact with a scope change beyond the original security boundary.
Affected Products
- Apple iOS and iPadOS prior to 26.3
- Apple macOS Sequoia prior to 15.7.4, macOS Sonoma prior to 14.8.4, and macOS Tahoe prior to 26.3
- Apple watchOS prior to 26.3
Discovery Timeline
- 2026-02-11 - CVE-2026-20667 published to the National Vulnerability Database
- 2026-04-02 - Last updated in NVD database
Technical Details for CVE-2026-20667
Vulnerability Analysis
The vulnerability resides in the sandbox enforcement logic shared across Apple operating systems. The Apple sandbox is a mandatory access control mechanism that restricts what system resources, files, and inter-process communication endpoints an application can reach. A logic flaw in the enforcement checks allowed an application to perform operations that should have been denied by sandbox policy.
The issue is categorized as a Protection Mechanism Failure [CWE-693]. Rather than a memory corruption bug, the root cause is a flawed decision path within the sandbox enforcement code. Apple's fix introduces improved checks that close the gap permitting the unauthorized action.
Exploitation requires the attacker to first deliver and execute code within a sandboxed app context. Once running, the app can leverage the flawed check to access resources outside its container, including files, system services, or other process boundaries normally blocked by the sandbox profile.
Root Cause
The root cause is incomplete validation in the sandbox subsystem. Specific implementation details have not been published by Apple beyond the description that a logic issue was addressed with improved checks. The shared codebase across iOS, iPadOS, macOS, and watchOS explains the broad product scope.
Attack Vector
The attack vector is local. An attacker needs code execution inside a sandboxed application, which is commonly achieved through a malicious App Store or sideloaded app, a compromised legitimate app, or by chaining this issue with a prior remote vulnerability such as a WebKit or messaging client exploit. No user interaction is required once the malicious app is running. The scope change indicates that successful exploitation grants access to resources outside the original sandbox boundary.
No verified public proof-of-concept code is currently available, and the vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog.
Detection Methods for CVE-2026-20667
Indicators of Compromise
- Unexpected file access by sandboxed applications to paths outside their container, such as ~/Library/, /private/var/, or other users' data directories
- Sandboxed processes spawning child processes or invoking XPC services they do not normally communicate with
- macOS Unified Log entries from sandboxd or kernel reporting policy violations or denied operations followed by successful access
Detection Strategies
- Monitor endpoint telemetry for sandboxed applications performing file, network, or IPC operations inconsistent with their declared entitlements
- Correlate process lineage to identify App Store or third-party apps that escalate to access protected system locations
- Review crash reports and sandboxd logs for repeated policy denials that may indicate exploitation attempts preceding a successful escape
Monitoring Recommendations
- Ingest macOS Unified Logs and EndpointSecurity events into a centralized analytics platform for behavioral analysis across the fleet
- Track installed application inventory and versions to identify devices still running vulnerable OS builds
- Alert on any sandboxed process accessing Keychain, TCC-protected directories, or other sensitive resources outside its entitlement set
How to Mitigate CVE-2026-20667
Immediate Actions Required
- Update all Apple devices to iOS 26.3, iPadOS 26.3, macOS Sequoia 15.7.4, macOS Sonoma 14.8.4, macOS Tahoe 26.3, or watchOS 26.3
- Inventory the fleet using mobile device management to identify devices below the patched versions and prioritize remediation
- Restrict installation of untrusted or sideloaded applications until patching is complete
Patch Information
Apple released fixes in iOS 26.3, iPadOS 26.3, macOS Sequoia 15.7.4, macOS Sonoma 14.8.4, macOS Tahoe 26.3, and watchOS 26.3. Refer to the Apple Security Update Advisory for iOS and iPadOS 26.3, macOS Sequoia 15.7.4, macOS Sonoma 14.8.4, macOS Tahoe 26.3, and watchOS 26.3 for full release details.
Workarounds
- No vendor-supplied workaround exists; updating to the patched OS version is the only supported remediation
- Limit App Store and third-party app installations on managed devices through MDM configuration profiles until patches are deployed
- Enforce Lockdown Mode on high-risk user devices to reduce the attack surface available to malicious applications
# Verify installed macOS version meets the patched build
sw_vers -productVersion
# Check iOS/iPadOS version via MDM query or on-device:
# Settings > General > About > Software Version
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
