CVE-2026-58701: Trusty SMC Race Condition Vulnerability

CVE-2026-58701 Overview

CVE-2026-58701 is an out-of-bounds write vulnerability caused by a race condition in the trusty_dputc function of generic-arm64-smcall.c. The flaw exists in the Trusty Trusted Execution Environment (TEE) code used on Android devices. Local attackers with low privileges can exploit the race condition to escalate privileges to System-level execution. User interaction is not required for exploitation.

Critical Impact
Successful exploitation grants System execution privileges on affected Android devices, allowing an attacker to bypass application sandboxing and access privileged resources.

Affected Products

Android (Pixel) devices referenced in the Android Security Bulletin September 2026
Trusty TEE component generic-arm64-smcall.c
Devices shipping the vulnerable Trusty trusty_dputc implementation

Discovery Timeline

2026-09-15 - CVE-2026-58701 published to NVD
2026-09-16 - Last updated in NVD database

Technical Details for CVE-2026-58701

Vulnerability Analysis

The vulnerability resides in trusty_dputc, a debug character output routine in the Trusty Secure Monitor Call (SMC) handling layer on ARM64. The function performs writes to a shared buffer without adequate synchronization between concurrent callers. Two threads racing through the same code path can invoke the write past the buffer boundary. The result is memory corruption within a privileged context of the Trusted Execution Environment. Because the exploited context runs with System privileges, corruption can be leveraged to alter control data used by higher-privileged components. The weakness is classified as [CWE-362] — concurrent execution using shared resource with improper synchronization (race condition).

Root Cause

The root cause is missing or insufficient locking around a shared buffer index or pointer used by trusty_dputc. When multiple execution contexts invoke the function simultaneously, the bounds check and the subsequent write are not atomic. One thread can pass the check while another advances the index, causing the write to land outside the allocated buffer. This TOCTOU (Time-of-Check Time-of-Use) pattern produces the out-of-bounds write.

Attack Vector

Exploitation requires local access and low privileges on the device. An attacker running unprivileged code triggers concurrent SMC invocations that reach trusty_dputc, winning the race to corrupt memory adjacent to the target buffer. Attack complexity is high because it depends on timing conditions inherent to the race. No user interaction is required. Refer to the Android Security Bulletin September 2026 for vendor technical details.

Detection Methods for CVE-2026-58701

Indicators of Compromise

Unexpected Trusty TEE crashes or kernel panics referencing trusty_dputc or generic-arm64-smcall.c in device logs.
Anomalous SMC call bursts from unprivileged processes observed in kernel tracing.
Processes gaining System-level capabilities without matching install or update events.

Detection Strategies

Monitor dmesg and logcat for repeated Trusty exceptions or memory faults originating in the SMC path.
Baseline SMC call frequency per UID and alert on statistical outliers indicative of race-window brute forcing.
Correlate privilege transitions with prior Trusty error events to identify successful escalation attempts.

Monitoring Recommendations

Aggregate mobile device telemetry into a centralized analytics platform to identify TEE-level anomalies across the fleet.
Enforce mobile device management (MDM) policies that report Android security patch level compliance.
Track installation of unknown or sideloaded applications that could stage local exploitation.

How to Mitigate CVE-2026-58701

Immediate Actions Required

Apply the September 2026 Android security patch level or later to all affected Pixel and Android devices.
Inventory devices that cannot receive the patch and restrict their access to sensitive corporate resources.
Enforce Google Play Protect and disallow sideloaded applications from untrusted sources.

Patch Information

Google released fixes as part of the Android Security Bulletin September 2026. Devices at security patch level 2026-09-01 or later contain the corrected trusty_dputc implementation with proper synchronization around the shared buffer write path.

Workarounds

No official workarounds exist; patching is the only supported remediation.
Restrict installation of untrusted applications to reduce the local attack surface until patching completes.
Use MDM policies to enforce minimum Android security patch levels for enrolled devices.

bash

# Verify Android security patch level on an enrolled device
adb shell getprop ro.build.version.security_patch
# Expected output: 2026-09-01 or later