CVE-2025-21440 Overview
CVE-2025-21440 is a memory corruption vulnerability affecting the Qualcomm WLAN driver across a broad range of Snapdragon, FastConnect, and QCA chipset firmware. The flaw occurs when a user-space process invokes an IOCTL call to write board data to the WLAN driver. Insufficient validation of the user-supplied input results in an out-of-bounds write ([CWE-787]) inside kernel memory. A local, authenticated attacker can trigger the condition to corrupt kernel structures and potentially escalate privileges on affected devices.
Critical Impact
A local low-privileged attacker can corrupt kernel memory through a WLAN driver IOCTL, leading to loss of confidentiality, integrity, and availability on the affected device.
Affected Products
- Qualcomm FastConnect 6200/6700/6800/6900/7800 WLAN subsystems
- Qualcomm Snapdragon 7c, 7c Gen 2, 7c+ Gen 3, 8c, and 8cx Compute Platforms
- Qualcomm QCA6391, QCA6420, QCA6430, QCA1062/1064, QCA2062/2064/2065/2066, QCM/QCS 5430 and 6490, SC8180X+SDX55, SC8380XP, SM6250, AQT1000, and WCD/WSA audio codec firmware
Discovery Timeline
- 2025-04-07 - CVE-2025-21440 published to NVD
- April 2025 - Qualcomm publishes the Qualcomm April 2025 Security Bulletin with patched firmware
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2025-21440
Vulnerability Analysis
The vulnerability is classified as an out-of-bounds write ([CWE-787]) in the Qualcomm WLAN kernel driver. It is reachable through an IOCTL interface exposed to user space that accepts board data intended to configure the wireless chipset. The driver does not adequately validate the length or structure of the caller-supplied buffer before copying it into a kernel-side destination. Writing past the destination boundary corrupts adjacent kernel memory, which an attacker can leverage to influence control-flow structures, function pointers, or heap metadata. Exploitation requires local access with low privileges but no user interaction.
Root Cause
The root cause is missing or insufficient bounds checking on IOCTL input describing WLAN board data. When user-space calls the driver's board-data write handler, the copied payload can exceed the target kernel buffer, producing a linear out-of-bounds write in the kernel address space.
Attack Vector
Exploitation requires a local process on the device with permission to open the WLAN driver's device node. The attacker crafts a malformed IOCTL payload targeting the board data write path. Because the corruption occurs in the kernel, successful exploitation can lead to arbitrary kernel memory writes, privilege escalation from an unprivileged app to a kernel-mode context, or a device-wide denial of service. No verified public proof-of-concept is available at this time. See the Qualcomm April 2025 Security Bulletin for vendor-supplied technical details.
Detection Methods for CVE-2025-21440
Indicators of Compromise
- Unexpected kernel panics or reboots referencing the Qualcomm WLAN driver (wlan, cnss, icnss) in dmesg or vendor crash logs
- Applications outside the platform WLAN service opening /dev/wlan or WLAN control device nodes and issuing board-data IOCTL codes
- KASAN or kernel memory sanitizer reports flagging out-of-bounds writes originating from WLAN driver handlers
Detection Strategies
- Audit installed firmware versions against Qualcomm's April 2025 bulletin to identify unpatched chipsets on managed devices
- Instrument device telemetry to detect anomalous IOCTL invocations against WLAN device nodes from non-system UIDs
- Correlate WLAN driver crash signatures with process ancestry to distinguish benign firmware faults from exploit attempts
Monitoring Recommendations
- Ingest Android or embedded Linux kernel logs into a central logging platform and alert on repeated WLAN driver faults from a single process
- Track OEM security patch level (ro.build.version.security_patch) and enforce a minimum patch level of April 2025 or later on managed endpoints
- Monitor for newly sideloaded or unmanaged applications on devices that ship with the affected Snapdragon or FastConnect chipsets
How to Mitigate CVE-2025-21440
Immediate Actions Required
- Apply the OEM firmware update that incorporates Qualcomm's April 2025 security patches to all affected devices
- Inventory endpoints and mobile devices using the FastConnect, QCA, QCM/QCS, WCD, WSA, and Snapdragon Compute chipsets listed above
- Restrict installation of untrusted applications on devices that cannot yet receive patched firmware
Patch Information
Qualcomm addressed CVE-2025-21440 in the Qualcomm April 2025 Security Bulletin. Patched firmware is delivered to end users through OEM and carrier updates; administrators should confirm the patch has been merged into the specific device build in use, since availability varies by manufacturer and model.
Workarounds
- No official vendor workaround exists; firmware patching through the OEM is the supported remediation path
- Enforce mobile device management policies that block sideloading and require the April 2025 (or later) security patch level before granting access to sensitive resources
- Where feasible, isolate legacy devices that cannot be patched into a network segment with restricted access to corporate assets
# Verify Android security patch level on managed devices
adb shell getprop ro.build.version.security_patch
# Expected value: 2025-04-01 or later
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
