CVE-2025-21458: Qualcomm Fastconnect 6900 Use-After-Free

CVE-2025-21458 Overview

CVE-2025-21458 is a memory corruption vulnerability affecting multiple Qualcomm chipsets and firmware components. The flaw occurs when the IOCTL (Input/Output Control) interface is invoked to map and unmap buffers simultaneously, creating a race condition classified as a use-after-free issue [CWE-416]. Qualcomm disclosed the vulnerability in its August 2025 Security Bulletin, and it impacts a broad range of Snapdragon mobile platforms, automotive SoCs, connectivity chipsets, and audio codecs. Successful exploitation allows a local attacker with low privileges to compromise the confidentiality, integrity, and availability of the affected device.

Critical Impact
A local, low-privileged attacker can trigger memory corruption in kernel-mode driver code, potentially leading to arbitrary code execution or privilege escalation on affected Qualcomm-based devices.

Affected Products

Qualcomm FastConnect 6900 firmware
Qualcomm Snapdragon 888 5G Mobile Platform and Snapdragon 888+ 5G Mobile Platform (SM8350-AC) firmware
Qualcomm automotive and IoT SoC firmware (SA8255P, SA8620P, SA8650P, SA8775P, SA9000P, SA7255P, SA7775P, QAM8255P, QAM8650P, QAM8775P, SW5100, SW5100P, QCA6174A, QCA6698AQ, QCA6797AQ, WCD9380, WCD9385, WCN3980, WCN3988, WSA8830, WSA8835)

Discovery Timeline

2025-08-06 - CVE-2025-21458 published to NVD
August 2025 - Qualcomm publishes the August 2025 Security Bulletin addressing the issue
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-21458

Vulnerability Analysis

The vulnerability resides in a Qualcomm kernel driver that exposes an IOCTL interface for buffer management. When two threads invoke the map and unmap operations concurrently against the same buffer, the driver fails to serialize access to the underlying buffer metadata. This produces a use-after-free (UAF) condition [CWE-416], where one thread frees a buffer while another thread still holds a stale reference to it. Subsequent operations on the freed structure corrupt kernel memory. An attacker with local access and the ability to open the driver interface can trigger the race deterministically by repeatedly issuing paired IOCTL calls from separate threads.

Root Cause

The root cause is missing or insufficient synchronization around buffer lifecycle state transitions in the IOCTL handler. Map and unmap paths share reference-counted buffer descriptors without holding a common lock during the decrement, free, and dereference operations. This TOCTOU-like window allows one path to release resources while another path continues to operate on them.

Attack Vector

Exploitation requires local access with low privileges (PR:L) on the target device and no user interaction. On Android-based Snapdragon devices, a malicious application with permission to open the vulnerable device node can trigger the race. On automotive and IoT targets, the attacker must already have code execution in a userspace context with access to the driver. Because the corruption occurs in kernel memory, successful exploitation can escalate privileges from a sandboxed application to kernel-level code execution.

// No verified proof-of-concept is publicly available.
// The vulnerability is triggered by concurrent map/unmap IOCTL calls
// against the affected Qualcomm driver interface from two threads.
// Refer to the Qualcomm August 2025 Security Bulletin for details.

Detection Methods for CVE-2025-21458

Indicators of Compromise

Unexpected kernel panics, watchdog resets, or SIGBUS/SIGSEGV crashes originating from Qualcomm driver modules on affected devices.
Kernel logs (dmesg, logcat -b kernel) showing use-after-free, KASAN, or slab corruption reports referencing Qualcomm buffer management functions.
Unsigned or unexpected applications opening privileged Qualcomm device nodes (for example, /dev/kgsl-3d0 or vendor-specific IOCTL endpoints).

Detection Strategies

Monitor for repeated IOCTL invocations from a single process against Qualcomm driver device nodes, particularly paired map/unmap operations issued from multiple threads.
Enable kernel address sanitizer (KASAN) or vendor equivalent on development and staging hardware to surface UAF conditions during testing.
Review Android system crash reports and Automotive Grade Linux telemetry for driver-level faults correlated with third-party application installs.

Monitoring Recommendations

Aggregate device crash telemetry and correlate faults against the Qualcomm driver modules identified in the Qualcomm August 2025 Security Bulletin.
Track patch-level (ro.build.version.security_patch) across the fleet and alert on devices still reporting a pre-August 2025 Android security patch level.
For managed automotive and IoT deployments, integrate device logs into a centralized SIEM and alert on kernel-mode faults in Qualcomm subsystems.

How to Mitigate CVE-2025-21458

Immediate Actions Required

Apply the Qualcomm firmware update referenced in the August 2025 Security Bulletin as soon as the OEM makes it available for the affected device model.
Inventory all fleet devices using the affected Snapdragon, FastConnect, QCA, WCD, WCN, WSA, SA, QAM, or SW-series chipsets and prioritize patch rollout.
Restrict installation of untrusted third-party applications on affected mobile and automotive devices until patches are deployed.

Patch Information

Qualcomm has released firmware fixes for all affected components. Refer to the Qualcomm August 2025 Security Bulletin for the authoritative list of patched versions. Device OEMs (Samsung, Google, Xiaomi, automotive vendors, and others) must integrate these fixes into their downstream firmware images before end users receive the update.

Workarounds

No official workaround exists; Qualcomm recommends applying the vendor patch.
Reduce local attack surface by enforcing application allowlisting and restricting sideloading on managed devices.
Where feasible, apply SELinux or vendor MAC policies to limit which processes can open the vulnerable driver device nodes.

bash

# Verify Android security patch level on affected devices
adb shell getprop ro.build.version.security_patch

# Expected output should be 2025-08-01 or later once the patch is applied