CVE-2026-56923 Overview
CVE-2026-56923 is a race condition vulnerability in the handle_unmap_req function of tipc_virtio_dev.c, a Trusted Inter-Process Communication (TIPC) virtio driver component in Android. Concurrent execution paths can trigger memory corruption during unmap request handling. Successful exploitation results in local privilege escalation without requiring user interaction or additional execution privileges. The flaw is classified under [CWE-362] (Concurrent Execution using Shared Resource with Improper Synchronization).
Critical Impact
Local attackers with existing privileges can corrupt kernel memory through a race condition, achieving privilege escalation on affected Android devices without user interaction.
Affected Products
- Android devices incorporating the tipc_virtio_dev driver
- Pixel devices per the September 2026 Android Security Bulletin
- Downstream OEM builds sharing the affected TIPC virtio component
Discovery Timeline
- 2026-09-15 - CVE-2026-56923 published to NVD
- 2026-09-16 - Last updated in NVD database
Technical Details for CVE-2026-56923
Vulnerability Analysis
The vulnerability resides in handle_unmap_req, a handler within the TIPC virtio device driver (tipc_virtio_dev.c). TIPC provides a message-passing channel between Android and the Trusty Trusted Execution Environment (TEE). The handle_unmap_req routine processes requests to unmap shared memory regions previously registered for TEE communication.
Because the unmap logic lacks sufficient synchronization, two threads can operate on the same shared memory descriptor concurrently. One thread may free or mutate a memory object while another thread still references it. This produces memory corruption in kernel context.
The issue requires local access and high existing privileges but no user interaction. Exploitation yields local escalation of privilege, granting the attacker access above their original permission level.
Root Cause
The root cause is improper synchronization when handling shared resources during unmap operations. The handler does not adequately serialize access to shared state, permitting a Time-of-Check to Time-of-Use (TOCTOU) window. Concurrent invocations of the unmap path race against each other or against parallel map/reference operations.
Attack Vector
An attacker with local access and elevated privileges must invoke the vulnerable ioctl path repeatedly while racing a second thread that operates on the same TIPC shared memory descriptor. Successful timing of the race produces a corrupted kernel object, which the attacker can leverage to escalate to a higher privilege context. Technical exploitation details are described in the Android Security Bulletin September 2026.
Detection Methods for CVE-2026-56923
Indicators of Compromise
- Unexpected kernel panics or Oops messages referencing tipc_virtio_dev or handle_unmap_req in dmesg and logcat
- Repeated concurrent ioctl calls from a single non-privileged process to the TIPC device node
- KASAN reports indicating use-after-free or slab corruption in TIPC-related allocations
Detection Strategies
- Monitor Android kernel logs for driver faults or SELinux denials involving /dev/trusty-ipc-dev* device nodes
- Enable and review Kernel Address Sanitizer (KASAN) output on test builds to surface race-triggered corruption
- Correlate process behavior showing rapid, threaded ioctl bursts against the TIPC endpoint with subsequent privilege changes
Monitoring Recommendations
- Ingest Android logcat and kernel telemetry into a centralized analytics platform for anomaly detection on driver crashes
- Alert on unexpected process privilege transitions on managed Android endpoints
- Track patch level (ro.build.version.security_patch) across the device fleet to confirm September 2026 or later coverage
How to Mitigate CVE-2026-56923
Immediate Actions Required
- Apply the September 2026 Android security patch level (2026-09-05 or later) to all affected devices
- Prioritize patch deployment on Pixel devices and OEM builds referenced in the Android Security Bulletin
- Restrict installation of untrusted applications that could invoke the vulnerable ioctl path
Patch Information
Google addressed CVE-2026-56923 in the September 2026 Android Security Bulletin. Device manufacturers must ship the corresponding patch level to end users. Refer to the Android Security Bulletin September 2026 for source patch references and affected components.
Workarounds
- No official workaround is documented; patching is the required remediation
- Reduce exposure by enforcing Play Protect and blocking sideloaded applications on managed devices
- Apply mobile device management (MDM) policies that prevent installation of untrusted apps until patched builds are deployed
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.