CVE-2026-21381: Qualcomm AR8035 Firmware DOS Vulnerability

CVE-2026-21381 Overview

CVE-2026-21381 is a Denial of Service vulnerability affecting Qualcomm chipset firmware that occurs when processing service data frames over Neighborhood Awareness Network (NAN) protocol connections. The vulnerability is triggered when a device receives a service data frame with excessive length during the device matching phase, resulting in a transient denial of service condition.

This vulnerability impacts a wide range of Qualcomm products including Snapdragon mobile platforms, FastConnect wireless modules, and various firmware components used in smartphones, IoT devices, and networking equipment. The flaw is classified under CWE-126 (Buffer Over-read), indicating the firmware fails to properly validate the length of incoming NAN service data frames before processing.

Critical Impact

Attackers can remotely trigger denial of service conditions on affected Qualcomm-based devices by sending specially crafted NAN protocol frames, potentially disrupting device connectivity and availability without requiring authentication.

Affected Products

• Qualcomm Snapdragon 8 Elite, Snapdragon 8 Gen 3, Snapdragon 6/7 Series Mobile Platforms
• Qualcomm FastConnect 6200, 6700, 6900, 7800 Wi-Fi/Bluetooth Modules
• Qualcomm WCN Series (WCN3988, WCN6450, WCN6650, WCN6755, WCN7860/7861/7880/7881)
• Qualcomm Snapdragon X72/X75 5G Modem-RF Systems
• Qualcomm AR8035, QCA6391, QCA6698AU, and numerous QCA/QCN networking chipsets

Discovery Timeline

• April 6, 2026 - CVE-2026-21381 published to NVD
• April 8, 2026 - Last updated in NVD database

Technical Details for CVE-2026-21381

Vulnerability Analysis

The vulnerability exists in the NAN (Neighborhood Awareness Network) protocol implementation within Qualcomm chipset firmware. NAN is a Wi-Fi Alliance specification that enables devices to discover nearby services and devices in a power-efficient manner without requiring an access point or cellular connection.

The flaw manifests during the device matching phase of NAN connections, where the firmware processes service data frames exchanged between devices. When a malformed frame with an excessive length value is received, the firmware attempts to read beyond allocated buffer boundaries, triggering a buffer over-read condition (CWE-126).

This vulnerability can be exploited remotely over the network without authentication. An attacker within wireless range can craft malicious NAN service data frames that cause affected devices to enter a transient denial of service state, disrupting wireless connectivity.

Root Cause

The root cause is insufficient input validation in the NAN protocol handler when processing the length field of incoming service data frames. The firmware does not adequately verify that the declared frame length matches the actual received data or falls within expected bounds. This missing boundary check allows an attacker to trigger a buffer over-read by specifying an excessive length value in the frame header, causing the firmware to access memory beyond the allocated buffer.

Attack Vector

The attack can be executed remotely over the network by any device within wireless range of the target. The attacker does not require any privileges or authentication on the target device. The attack flow involves:

1. The attacker enables NAN discovery mode on their device or uses a custom wireless tool
2. The attacker crafts a malicious NAN service data frame with an excessive length value in the header
3. The malformed frame is transmitted over the air to nearby devices with NAN enabled
4. Affected Qualcomm-based devices receive and attempt to process the frame
5. The buffer over-read condition triggers, causing a transient denial of service

The vulnerability does not result in data confidentiality or integrity impacts, but can repeatedly disrupt device availability while the attack continues.

Detection Methods for CVE-2026-21381

Indicators of Compromise

• Unexpected Wi-Fi or wireless connectivity interruptions on Qualcomm-based devices
• System logs showing NAN protocol errors or wireless subsystem crashes
• Devices repeatedly losing NAN connections or experiencing service discovery failures
• Wireless controller or access point logs showing unusual NAN frame patterns

Detection Strategies

• Monitor wireless network traffic for anomalous NAN protocol frames with unusual length values
• Implement wireless intrusion detection systems (WIDS) with rules to detect malformed NAN frames
• Track device stability metrics to identify patterns of wireless subsystem restarts or connectivity drops
• Review system diagnostic logs for firmware crashes related to NAN or Wi-Fi subsystems

Monitoring Recommendations

• Enable verbose logging on wireless infrastructure to capture NAN protocol events
• Deploy wireless sensors capable of monitoring 802.11 management and action frames
• Establish baseline metrics for device wireless connectivity to detect anomalies
• Configure alerting on repeated wireless subsystem errors or unexpected device reboots

How to Mitigate CVE-2026-21381

Immediate Actions Required

• Review the Qualcomm Security Bulletin April 2026 for affected products and patch availability
• Apply firmware updates from device manufacturers (OEMs) as they become available
• Consider disabling NAN functionality on affected devices where the feature is not required
• Implement network segmentation to limit exposure of affected devices to untrusted wireless networks

Patch Information

Qualcomm has addressed this vulnerability in their April 2026 security bulletin. Organizations should monitor their device manufacturers for firmware updates that incorporate the Qualcomm patches. The fix involves adding proper length validation for NAN service data frames to prevent buffer over-read conditions.

For detailed patch information and affected chipset versions, refer to the Qualcomm Security Bulletin April 2026.

Workarounds

• Disable Neighborhood Awareness Network (NAN) / Wi-Fi Aware functionality on devices where it is not operationally required
• Limit device exposure to untrusted wireless environments until patches are applied
• Use enterprise wireless networks with strong access controls to reduce exposure to rogue devices
• Monitor affected devices for signs of exploitation and isolate any exhibiting symptoms

# Android devices - Check Wi-Fi Aware status (requires ADB access)
adb shell cmd wifi status | grep -i aware

# To disable Wi-Fi Aware programmatically, application code or MDM policy may be required
# Consult device manufacturer documentation for specific disable procedures