CVE-2023-21263: Google Android Privilege Escalation Flaw

CVE-2023-21263 Overview

CVE-2023-21263 is an out-of-bounds write vulnerability in the OSMMapPMRGeneric function of pmr_os.c, a component used by the Android kernel graphics memory subsystem. The flaw arises from an uncaught exception that allows memory to be written outside the intended buffer boundaries. A local attacker can leverage this issue to escalate privileges to the kernel without user interaction and without requiring additional execution permissions. Google addressed the issue in the Android Security Bulletin December 2023.

Critical Impact
Successful exploitation grants kernel-level privileges on affected Android devices, allowing full device compromise without user interaction.

Affected Products

Google Android (kernel pmr_os.c component)
Devices shipping with the vulnerable PowerVR Rogue (pmr_os) kernel module
Android builds prior to the December 2023 security patch level

Discovery Timeline

2023-12-01 - Google releases the Android Security Bulletin addressing the issue
2023-12-04 - CVE-2023-21263 published to NVD
2024-11-21 - Last updated in NVD database

Technical Details for CVE-2023-21263

Vulnerability Analysis

The vulnerability resides in OSMMapPMRGeneric, a function inside pmr_os.c that handles memory mapping for Physical Memory Resources (PMR) within the kernel graphics stack. The function fails to handle an exception condition during the mapping operation. This uncaught exception leads to an out-of-bounds write within kernel memory. An attacker executing code with normal user-level privileges on the device can trigger the faulty mapping path. The resulting memory corruption permits modification of kernel structures and escalation to kernel context.

Root Cause

The defect is an unhandled exception in the PMR memory-mapping routine. When the exception fires, control flow continues without proper bounds enforcement, and a write occurs beyond the intended allocation. The CWE classification is listed as NVD-CWE-noinfo, but the behavior aligns with an out-of-bounds write leading to kernel privilege escalation.

Attack Vector

Exploitation is local. A malicious application or process running on the device invokes the vulnerable mapping path through the graphics driver interface. No user interaction is required, and the attacker does not need elevated privileges before triggering the flaw. Once the out-of-bounds write occurs, the attacker can overwrite kernel state to achieve arbitrary kernel-mode execution.

No public proof-of-concept exploit is available, and the issue is not listed in the CISA Known Exploited Vulnerabilities catalog. Refer to the Android Security Bulletin December 2023 for vendor technical details.

Detection Methods for CVE-2023-21263

Indicators of Compromise

Unexpected kernel oops or panic entries referencing OSMMapPMRGeneric or pmr_os in device logs
Installation of untrusted applications immediately preceding kernel crashes or reboots
Processes obtaining kernel-level capabilities without a corresponding privileged binary execution

Detection Strategies

Audit installed Android applications against allow-lists and remove those from untrusted sources
Inspect dmesg and logcat output for repeated faults in graphics or PMR-related kernel modules
Compare device security patch level against the December 2023 Android patch baseline using ro.build.version.security_patch

Monitoring Recommendations

Enroll Android devices in a mobile threat defense or MDM platform that reports patch level compliance
Forward kernel crash telemetry from managed devices into a centralized logging or SIEM platform for anomaly review
Monitor for sideloaded APKs and abnormal use of graphics or ioctl-heavy system calls from user applications

How to Mitigate CVE-2023-21263

Immediate Actions Required

Apply the Android security patch level dated 2023-12-05 or later on all managed devices
Block installation of applications from unknown sources through MDM policy
Remove untrusted or unnecessary applications, especially those requesting graphics or DRM-related permissions

Patch Information

Google addressed CVE-2023-21263 in the Android Security Bulletin dated 2023-12-01. Devices reporting a security patch level of 2023-12-05 or later contain the fix. OEM update availability varies by device manufacturer and carrier. Consult the Android Security Bulletin December 2023 for the full list of fixes and references.

Workarounds

Restrict device usage to trusted, signed applications until the patch is deployed
Enforce Google Play Protect and disable installation from unknown sources
Replace unsupported devices that no longer receive security updates from the OEM

bash

# Verify the Android security patch level on a connected device
adb shell getprop ro.build.version.security_patch
# Expected output for patched devices: 2023-12-05 or later