CVE-2023-21399 Overview
CVE-2023-21399 is a high-severity vulnerability in Google Android that allows a local attacker to bypass cryptographic assurances. The flaw stems from a logic error in cryptographic code [CWE-327: Use of a Broken or Risky Cryptographic Algorithm]. Successful exploitation enables local escalation of privilege without requiring additional execution privileges or user interaction. Google addressed the issue in the Android Security Bulletin July 2023.
Critical Impact
A local attacker can bypass cryptographic protections to escalate privileges on affected Android devices, compromising confidentiality, integrity, and availability without user interaction.
Affected Products
- Google Android (per Pixel Security Bulletin, July 2023)
- Devices running unpatched Android builds prior to the July 2023 security patch level
- Google Pixel devices addressed by the July 2023 bulletin
Discovery Timeline
- 2023-07-13 - CVE-2023-21399 published to the National Vulnerability Database (NVD)
- 2024-11-21 - Last updated in NVD database
Technical Details for CVE-2023-21399
Vulnerability Analysis
The vulnerability resides in cryptographic logic within the Android platform. A logic error in the code path allows an attacker to bypass intended cryptographic assurances that normally protect sensitive operations or data boundaries. Because the bypass occurs in trusted cryptographic enforcement, it undermines the security guarantees that higher-level Android components rely on for privilege separation.
Exploitation requires only local access with low privileges. No user interaction is required, and the attack complexity is low. A locally executing application can leverage the flaw to elevate to privileges otherwise reserved for higher-trust components, achieving high impact across confidentiality, integrity, and availability.
Root Cause
The root cause is a logic error in the implementation of a cryptographic routine, categorized as [CWE-327]. The flawed logic permits operations to succeed under conditions where cryptographic validation should have rejected them. This converts a cryptographic correctness flaw into a privilege boundary failure.
Attack Vector
The attack vector is local. An adversary must execute code on the device, typically via a malicious or compromised application running with standard privileges. The exploit invokes the affected cryptographic interface in a way that triggers the logic error, yielding elevated privileges on the device. Google has not published exploit code, and no public proof-of-concept is currently available.
No verified code examples are available for this issue. Refer to the Android Security Bulletin July 2023 for vendor-provided technical context.
Detection Methods for CVE-2023-21399
Indicators of Compromise
- Unexpected applications running with elevated privileges or system-level capabilities on Android devices.
- Logcat entries showing anomalous use of cryptographic APIs from unprivileged processes.
- Installed applications requesting or obtaining permissions inconsistent with their declared manifest.
Detection Strategies
- Compare device security patch levels against the July 2023 Android Security Bulletin baseline using mobile device management (MDM) telemetry.
- Hunt for installed packages whose runtime UID or selinux context diverges from expected values after installation.
- Inspect application behavior for unauthorized access to keystore-protected material or restricted system services.
Monitoring Recommendations
- Enforce MDM policies that report ro.build.version.security_patch and alert on devices below the July 2023 patch level.
- Forward Android audit and selinux denial logs to a centralized logging or SIEM platform for retrospective analysis.
- Review enterprise app catalogs and sideloaded applications for unsigned or unverified packages that could host local exploits.
How to Mitigate CVE-2023-21399
Immediate Actions Required
- Apply the July 2023 Android security patch level (or later) to all managed Android devices.
- Identify devices reporting a security patch level earlier than 2023-07-01 and prioritize them for update or replacement.
- Restrict installation of untrusted applications through Google Play Protect and enterprise MDM allow-listing.
Patch Information
Google released fixes in the July 2023 Android Security Bulletin. Device manufacturers integrated the patches into their respective monthly updates. Administrators should confirm that managed devices report a security patch level of 2023-07-01 or later. Detailed vendor information is published in the Android Security Bulletin July 2023.
Workarounds
- No vendor-supplied workaround exists; patching is the only supported remediation.
- Limit exposure by blocking installation of untrusted or sideloaded applications via MDM policy.
- Retire or isolate end-of-life devices that no longer receive monthly Android security updates.
# Verify Android security patch level on a connected device
adb shell getprop ro.build.version.security_patch
# Expected output: 2023-07-01 or later
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
