CVE-2025-21456: Qualcomm AR8035 Race Condition Vulnerability

CVE-2025-21456 Overview

CVE-2025-21456 is a memory corruption vulnerability affecting a broad range of Qualcomm chipsets and firmware components. The flaw occurs while processing an IOCTL command when multiple threads concurrently invoke buffer map and unmap operations. This race condition triggers a use-after-free (CWE-416), which a local, low-privileged attacker can leverage to corrupt kernel memory. Successful exploitation impacts confidentiality, integrity, and availability on affected devices. Qualcomm disclosed and patched the issue in the August 2025 Security Bulletin.

Critical Impact
Local low-privileged attackers can trigger kernel memory corruption on Snapdragon-based mobile, automotive, wearable, and connectivity platforms, enabling potential privilege escalation to kernel context.

Affected Products

Qualcomm Snapdragon 888 and 888+ 5G Mobile Platforms and Snapdragon W5+ Gen 1 Wearable Platform
Qualcomm automotive platforms including SA8155P, SA8255P, SA8295P, SA8540P, SA8620P, SA8650P, SA8775P, and QAM8xxxP series
Qualcomm connectivity components including FastConnect 6900/7800, QCA6xxx Wi-Fi chipsets, WCD/WSA audio codecs, and Snapdragon X72/X75 5G Modem-RF Systems

Discovery Timeline

2025-08-06 - CVE-2025-21456 published to NVD
August 2025 - Qualcomm publishes patch in the Qualcomm August 2025 Security Bulletin
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-21456

Vulnerability Analysis

The vulnerability is a concurrency-induced use-after-free (CWE-416) inside a Qualcomm kernel driver's IOCTL handler responsible for buffer management. When two or more threads issue overlapping map and unmap requests against the same buffer object, the driver fails to serialize access to the underlying reference-counted allocation. One thread can free the buffer descriptor while another thread still holds and dereferences a pointer to it, producing memory corruption in kernel address space. Because the affected IOCTL interface is reachable from a local application context, attackers with only low privileges and no user interaction can drive the race. The impact spans confidentiality, integrity, and availability, which is consistent with kernel-mode compromise on the affected chipsets.

Root Cause

The root cause is missing or insufficient locking around the driver's map/unmap paths. The driver assumes that buffer lifetime operations are non-overlapping, but concurrent IOCTL calls invalidate that assumption and lead to a dangling kernel pointer being reused after free.

Attack Vector

Exploitation requires local access to an affected device with the ability to open the vulnerable driver's device node and issue IOCTL calls. An attacker spawns multiple threads that repeatedly map and unmap the same buffer to win the race window. Once the use-after-free is triggered, an attacker can groom kernel heap allocations to place attacker-controlled data into the freed slot and hijack control flow or corrupt privileged structures.

No verified public exploit or proof-of-concept code is available for CVE-2025-21456. See the Qualcomm August 2025 Security Bulletin for vendor-authored technical detail.

Detection Methods for CVE-2025-21456

Indicators of Compromise

Unexpected kernel panics, watchdog resets, or SIGBUS/SIGSEGV crashes referencing Qualcomm buffer or memory driver stacks.
Repeated IOCTL invocations from a single unprivileged process against Qualcomm graphics, camera, or memory driver device nodes within short time windows.
Kernel log entries (dmesg, logcat -b kernel) showing slab or use-after-free messages tied to Qualcomm driver symbols.

Detection Strategies

Enable and monitor KASAN or equivalent kernel address sanitizers on engineering builds to surface use-after-free conditions in Qualcomm driver paths during testing.
Baseline normal IOCTL call patterns per process and alert on high-frequency, multi-threaded map/unmap sequences from non-system UIDs.
Correlate device firmware versions against the Qualcomm August 2025 Security Bulletin patch level to identify unpatched fleet devices.

Monitoring Recommendations

Collect and centralize mobile device kernel logs and crash dumps for automotive and IoT deployments that use Snapdragon chipsets.
Track patch levels reported by MDM or telematics platforms and flag devices below the August 2025 Qualcomm bulletin baseline.
Monitor for anomalous crashes on in-vehicle infotainment, telematics, and wearable devices where local code execution primitives are otherwise rare.

How to Mitigate CVE-2025-21456

Immediate Actions Required

Apply the Qualcomm firmware update from the August 2025 Security Bulletin as delivered by the device OEM or platform integrator.
Inventory all Snapdragon-based endpoints, automotive units, wearables, and connectivity modules against the affected products list and prioritize the ones exposing local application execution.
Restrict installation of untrusted local applications on affected mobile and embedded devices until the patch is deployed.

Patch Information

Qualcomm addressed CVE-2025-21456 in the Qualcomm August 2025 Security Bulletin. Patches are distributed to OEMs and must be integrated into downstream Android, automotive, and embedded firmware images. Contact the device manufacturer for the specific build that incorporates the August 2025 Qualcomm patch level.

Workarounds

Reduce local attack surface by disabling sideloading and enforcing application allow-listing on affected devices.
Where feasible, restrict access permissions on Qualcomm driver device nodes to system UIDs only via SELinux or platform policy.
Isolate high-value automotive and industrial endpoints from user-installable workloads until firmware containing the fix is deployed.

bash

# Verify current vendor security patch level on an Android/Snapdragon device
adb shell getprop ro.vendor.build.security_patch
# Expected: 2025-08-01 or later to include the CVE-2025-21456 fix