CVE-2025-48621 Overview
CVE-2025-48621 is a local privilege escalation vulnerability in the Android framework. The flaw resides in DefaultTransitionHandler.java, where an insecure default configuration allows a tapjacking attack. A local, low-privileged application can exploit the weakness to elevate privileges without requiring additional execution rights. Exploitation requires user interaction, as the attack relies on the victim performing a tap gesture during a UI transition.
Google addressed the issue in the Android Security Bulletin dated December 1, 2025. Affected releases include Android 13, 14, 15, and 16. The vulnerability is tracked under CWE-1188: Insecure Default Initialization of Resource.
Critical Impact
A malicious app can hijack taps during system transitions to gain elevated privileges on unpatched Android devices without requesting sensitive permissions.
Affected Products
- Google Android 13.0
- Google Android 14.0
- Google Android 15.0 and 16.0
Discovery Timeline
- 2025-12-08 - CVE-2025-48621 published to NVD
- December 2025 - Fix published in the Android Security Bulletin December 2025
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2025-48621
Vulnerability Analysis
The vulnerability originates in DefaultTransitionHandler.java, part of the Android framework responsible for animating window transitions between activities and tasks. During a transition, overlay windows can be drawn on top of the target activity because the handler ships with an insecure default that does not filter obscured touch events. An attacker-controlled application can time a transparent overlay to appear over a privileged UI, tricking the user into tapping a control that grants permissions or performs sensitive actions.
Tapjacking, a mobile-specific form of UI redressing, weaponizes this behavior. Because the exploited component runs within the system\ing process privilege boundary during the transition, taps forwarded to the underlying activity execute in a context the attacker cannot normally reach. The result is local escalation of privilege from an unprivileged app.
Root Cause
The root cause is an insecure default configuration [CWE-1188]. DefaultTransitionHandler did not set the FLAG_WINDOW_IS_OBSCURED or FLAG_WINDOW_IS_PARTIALLY_OBSCURED protections on transition surfaces, nor did it apply setFilterTouchesWhenObscured(true) on affected views. Overlay windows drawn by a third-party app were therefore able to intercept or mask user input directed at privileged system UI.
Attack Vector
Exploitation is local and requires an installed malicious application plus user interaction. The attacker publishes an app that requests the SYSTEM_ALERT_WINDOW permission or uses a benign overlay primitive, then draws a deceptive interface aligned with a system transition. When the user taps the overlay, the tap is delivered to the underlying privileged control. No additional execution privileges are required beyond installation of the malicious app. See the Android framework patch commit and the native framework update for the exact code paths.
Detection Methods for CVE-2025-48621
Indicators of Compromise
- Installed applications holding the SYSTEM_ALERT_WINDOW or TYPE_APPLICATION_OVERLAY permission that were not vetted by the enterprise app catalog.
- Applications that draw overlays synchronized to activity transitions, particularly against Settings, package installer, or accessibility prompts.
- Unexpected grants of runtime permissions or accessibility service enablement following recent app installs.
Detection Strategies
- Inventory installed apps on managed Android fleets and flag any package requesting overlay permissions without an approved business justification.
- Monitor MDM telemetry for accessibility service or Device Admin activations that occur shortly after new app installs.
- Correlate Android security patch level (ro.build.version.security_patch) against the December 1, 2025 baseline to identify vulnerable devices.
Monitoring Recommendations
- Ingest Android Enterprise and MDM logs into a central analytics pipeline to track permission grants and overlay usage across the fleet.
- Alert when apps outside the approved catalog request SYSTEM_ALERT_WINDOW or bind to AccessibilityService.
- Track sideloaded APK installations and unknown source enablement events, as these precede most tapjacking exploitation attempts.
How to Mitigate CVE-2025-48621
Immediate Actions Required
- Apply the December 2025 Android security patch level (2025-12-01 or later) to all Android 13, 14, 15, and 16 devices.
- Enforce patch-level compliance through MDM policies and block non-compliant devices from accessing corporate resources.
- Revoke SYSTEM_ALERT_WINDOW and accessibility permissions from any app that does not require them for a documented business purpose.
Patch Information
Google released fixes in the Android Security Bulletin December 2025. The framework changes are documented in the platform/frameworks/base commit 6d1697c9 and the platform/frameworks/native commit cc34c7b4. OEM firmware timelines vary; consult the device manufacturer for delivery schedules.
Workarounds
- Disable installation from unknown sources on managed devices to reduce the malicious app supply chain risk.
- Restrict the SYSTEM_ALERT_WINDOW permission via enterprise policy where the Android version supports runtime permission management.
- Educate users to cancel unexpected UI transitions and to review app permission requests before granting.
# Verify Android security patch level on a device
adb shell getprop ro.build.version.security_patch
# Expected output for patched devices: 2025-12-01 or later
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
