CVE-2026-56915: Bigo Worker Thread Race Condition Vulnerability

CVE-2026-56915 Overview

CVE-2026-56915 is a race condition vulnerability in the bigo_worker_thread function of bigo.c, a component associated with the Android platform. The flaw enables local privilege escalation to System-level execution without user interaction. Because exploitation occurs entirely within the local kernel context, an attacker must already hold elevated privileges on the device to trigger the race. The issue is tracked under CWE-362: Concurrent Execution using Shared Resource with Improper Synchronization and is addressed in the Android Security Bulletin September 2026.

Critical Impact
Successful exploitation grants System execution privileges on affected Android devices, undermining the platform's privilege separation model.

Affected Products

Android platform components including the bigo driver (bigo.c)
Pixel devices addressed in the September 2026 Android Security Bulletin
Downstream Android distributions incorporating the vulnerable bigo_worker_thread code path

Discovery Timeline

2026-09-15 - CVE-2026-56915 published to NVD
2026-09-16 - Last updated in NVD database

Technical Details for CVE-2026-56915

Vulnerability Analysis

The vulnerability resides in the bigo_worker_thread function within bigo.c. The function operates on shared resources without adequate synchronization, allowing concurrent execution paths to interfere with one another. An attacker who wins the race can manipulate shared state at a moment when it is expected to be consistent, corrupting kernel data structures or bypassing intended access controls.

The attack requires local access and high existing privileges, and no user interaction is needed. Exploitation complexity is elevated because the attacker must reliably win a narrow timing window in the worker thread's execution.

Root Cause

The root cause is improper synchronization between the worker thread and other execution contexts that access the same resources. Classified under [CWE-362], the flaw is a Time-of-Check to Time-of-Use (TOCTOU) style race where state validated at one point is mutated before being consumed. Missing or insufficient locking primitives permit interleaved execution that violates the driver's expected invariants.

Attack Vector

An attacker with local access and elevated privileges on the device triggers concurrent operations that reach the vulnerable code path in bigo_worker_thread. By repeatedly racing the worker thread against a controlled context, the attacker corrupts kernel memory or object state. Successful exploitation escalates from the attacker's initial privilege level to System execution privileges, breaking Android's sandbox model. Refer to the Android Security Bulletin September 2026 for technical details.

Detection Methods for CVE-2026-56915

Indicators of Compromise

Unexpected kernel log entries or dmesg warnings referencing the bigo driver or worker thread contention
Processes running with System privileges that were spawned from lower-privileged application contexts
Repeated, rapid invocations of ioctls or syscalls targeting the bigo device from a single application

Detection Strategies

Monitor Android device attestation and integrity signals for evidence of privilege boundary violations
Correlate application behavior with kernel-level anomalies exposed through Mobile Threat Defense telemetry
Track installed application versions against known-malicious packages that attempt kernel-driver abuse

Monitoring Recommendations

Enroll Android endpoints in a mobile threat management solution that reports patch level compliance
Alert on devices that fail to apply the September 2026 Android security patch level within organizational SLA
Review enterprise application inventories for apps requesting unusual access to device drivers or system services

How to Mitigate CVE-2026-56915

Immediate Actions Required

Apply the September 2026 Android security patch level to all affected Pixel and Android devices
Verify device patch level through Settings > About phone > Android security update on managed endpoints
Restrict sideloading and enforce enterprise application allowlists to reduce local attacker foothold

Patch Information

The vendor fix is delivered through the Android Security Bulletin September 2026. Devices at the 2026-09-01 security patch level or later incorporate the corrective synchronization changes in bigo.c. Organizations managing fleet devices should push the update through their mobile device management platform and confirm installation across enrolled endpoints.

Workarounds

No official workarounds are published; patching is the required remediation
Where patching is delayed, limit exposure by restricting installation of untrusted applications through MDM policy
Enforce work profile separation to constrain the blast radius of any local privilege escalation

bash

# Verify Android security patch level on a managed device via ADB
adb shell getprop ro.build.version.security_patch
# Expected output for remediated devices: 2026-09-01 or later