Shortcuts / App Intents Path + Symlink Sandbox Escape

← Improper Platform Usage

shortcuts_path_symlink_sandbox_escape   HARD

Description

Untrusted Shortcuts / App Intents input drives a file operation whose path is resolved through a symlink or a ../ traversal with no canonicalization, so the automation reaches files outside the app’s sandbox / container and exposes sensitive user data (iOS Shortcuts CVE-2026-20677 symlink race / CVE-2026-20653 path class).

How it works

Untrusted Shortcuts or App-Intents input drives a file operation whose path is resolved through a symlink or a “../” traversal with no canonicalization, so the automation reaches files outside the app’s sandbox or container (iOS Shortcuts CVE-2026-20677 symlink race / CVE-2026-20653 path class; the same class also appears when an App Intent’s perform() reads a caller-supplied path directly, CVE-2026-28995 / CVE-2026-64740). On device this plants a real symlink inside the container pointing outside it and seeds sensitive files beyond the sandbox, then reads them off the real filesystem. The secure path canonicalizes, resolves symlinks, and asserts the real path stays under the container root before reading.

How to exercise it. DVMA is the harness - open this module from the home index and tap the demo action. The screen ships the malicious input and simulates the attacker (e.g. the companion app, crafted intent, or scanned payload) in-process, and the evidence panel prints the proof. The Tools (optional) and Attack inputs below are only needed to reproduce the exploit end-to-end on a real device.

Exploit steps

1. Set up. Build DVMA with a flavor that enables the Improper Platform Usage category (e.g. --dart-define-from-file=config/flavors/dev.json) and run on an iOS simulator / a device you control. The demo needs no external tooling; for the optional on-device reproduction the relevant tools are: ifuse, afcclient.
2. Locate the target. From the home index, open Shortcuts / App Intents Path + Symlink Sandbox Escape (shortcuts_path_symlink_sandbox_escape). The How it works section above describes this module’s specific weakness; the screen states the intended-secure behavior and exposes the vulnerable action.
3. Exploit. From an attacker context (a crafted custom-URL-scheme / Universal Link, a malicious document provider / share extension, or a Shortcut), send the untrusted input to the handler and confirm the app performs the unsafe action (navigation, file/URL access, privileged operation) with no validation.
4. Observe the evidence. Trigger the vulnerable action and read the evidence panel - it prints the concrete proof (leaked value, accepted replay, executed payload, or unauthorized result).
5. Contrast with the secure path. Run the module’s secure/hardened action (where provided) and confirm the same attack is rejected - this is what a correct implementation should do.

Tools (optional)

• ifuse
• afcclient

Attack inputs

Payloads/artifacts you author for the on-device attack. The demo already ships and simulates these in-process (e.g. the malicious companion app / crafted intent is emulated inside the screen), so you only need to craft them to reproduce the exploit on a real device:

• crafted shortcut

Real-world references

Concrete public disclosures that match this vulnerability class:

• CVE-2026-20677 (iOS Shortcuts symlink race -> sandbox bypass, CVSS 9.0)
• About the security content of iOS 18.7.5 (CVE-2026-20653 Shortcuts path)
• CVE-2026-28995 (App Intents sandbox escape via a path parameter, iOS 26.5)
• CVE-2026-64740 (App Intents directory-path traversal -> sandbox escape, CWE-22, iOS 26.6)