CVE-2025-21438: Qualcomm Fastconnect Buffer Overflow Flaw

CVE-2025-21438 Overview

CVE-2025-21438 is a memory corruption vulnerability affecting a wide range of Qualcomm chipsets and firmware. The flaw occurs when an IOCTL call is invoked from user-space to read board data, and it is categorized as an out-of-bounds read [CWE-125]. A local attacker with low privileges can trigger the vulnerable code path without user interaction. Successful exploitation impacts confidentiality, integrity, and availability of the affected component. Qualcomm addressed the issue in the April 2025 security bulletin. Affected devices span mobile, compute, and audio platforms, including FastConnect, Snapdragon Compute, WCD audio codecs, and WSA smart speaker amplifiers.

Critical Impact
A local, low-privileged user can corrupt kernel memory through a crafted IOCTL request, enabling code execution or system compromise on affected Qualcomm platforms.

Affected Products

Qualcomm FastConnect 6200, 6700, 6900, and 7800 firmware
Qualcomm Snapdragon 7c, 8c, and 8cx Compute Platforms (multiple SKUs including SC7180, SC8180X, SC8280XP)
Qualcomm QCA6164/6174/6174A/6595AU/9377, QCM5430/6490, QCN7605/7606, QCS5430/6490, WCD9370/9375/9380/9385, and WSA8830/8835/8840/8845/8845H

Discovery Timeline

2025-04-07 - CVE-2025-21438 published to NVD
April 2025 - Qualcomm releases the Qualcomm Security Bulletin April 2025 addressing the issue
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-21438

Vulnerability Analysis

The vulnerability resides in the kernel-mode driver path that services an IOCTL request from user-space to read board data. When the driver processes the request, it reads beyond the bounds of an allocated buffer, producing an out-of-bounds read condition [CWE-125]. The improper bounds checking allows attacker-controlled input to influence the read length or offset, leading to memory corruption in kernel context. Because the affected code executes with elevated privilege, corrupted state can be leveraged to escalate privileges or destabilize the system.

Root Cause

The root cause is missing or insufficient validation of size and offset parameters supplied by user-space to the board-data IOCTL handler. The driver trusts user-controlled length fields when copying board data, allowing reads outside the intended buffer. This is a common firmware-driver pattern where the kernel-user boundary lacks strict sanitization of ioctl arguments.

Attack Vector

Exploitation requires local access and low privileges, such as those held by an unprivileged process or app on the affected device. No user interaction is required. The attacker issues a crafted IOCTL to the vulnerable device node, triggering the out-of-bounds read and subsequent memory corruption. See the Qualcomm Security Bulletin April 2025 for vendor-supplied technical details.

// No verified public proof-of-concept is available.
// The vulnerability is triggered by an ioctl() from user-space
// against the Qualcomm board-data driver interface, with
// attacker-controlled length or offset fields.

Detection Methods for CVE-2025-21438

Indicators of Compromise

Unexpected kernel panics, driver crashes, or dmesg entries referencing Qualcomm WLAN, audio, or board-data drivers
Unprivileged processes issuing repeated or malformed ioctl calls to Qualcomm device nodes
Anomalous device reboots or firmware watchdog resets on affected Snapdragon or FastConnect platforms

Detection Strategies

Monitor kernel logs for out-of-bounds read faults, KASAN reports, or oops traces originating from Qualcomm driver modules
Baseline expected ioctl behavior for board-data interfaces and alert on deviations from unprivileged callers
Correlate driver crash telemetry with process execution history to identify potential exploitation attempts

Monitoring Recommendations

Enable verbose kernel logging on test and production devices during the patch validation window
Ingest device telemetry into a centralized log platform for anomaly detection across the fleet
Track firmware and OTA update status to confirm affected devices have received the April 2025 Qualcomm patch

How to Mitigate CVE-2025-21438

Immediate Actions Required

Inventory all devices using the affected Qualcomm chipsets listed in the advisory
Apply the vendor firmware update referenced in the April 2025 Qualcomm Security Bulletin as soon as OEM builds are available
Restrict local access to untrusted users and unvetted third-party applications on affected devices
Enforce least-privilege policies for processes that can open Qualcomm device nodes

Patch Information

Qualcomm published fixes in the Qualcomm Security Bulletin April 2025. Device OEMs must incorporate the updated firmware and drivers into their OTA updates. Confirm patch adoption by validating firmware build numbers against OEM release notes.

Workarounds

No official workaround is published by Qualcomm; patching is the recommended remediation
Where patches are unavailable, limit installation of untrusted local applications that could invoke the vulnerable IOCTL
Restrict permissions on Qualcomm driver device nodes where the operating system allows configuration

bash

# Verify firmware/build level against OEM patch notes
adb shell getprop ro.build.version.security_patch
adb shell getprop ro.vendor.build.fingerprint