CVE-2025-21476: Qualcomm Qcs6490 Buffer Overflow Vulnerability

CVE-2025-21476 Overview

CVE-2025-21476 is a memory corruption vulnerability affecting a broad range of Qualcomm chipset firmware. The flaw occurs when parameters are passed to the Trusted Virtual Machine (TVM) during the handshake process. Qualcomm disclosed the issue in its September 2025 Security Bulletin, and it is classified under [CWE-120] (buffer copy without checking size of input).

An attacker with local, low-privileged access to an affected device can trigger memory corruption during the TVM handshake. Successful exploitation can compromise the confidentiality, integrity, and availability of the trusted execution environment on the device. The vulnerability spans dozens of Qualcomm mobile, compute, connectivity, and automotive platforms.

Critical Impact
Local attackers can corrupt memory in the Trusted Virtual Machine handshake path, potentially undermining the integrity of Qualcomm's trusted execution environment across a wide range of Snapdragon, WCN, and QCS platforms.

Affected Products

Qualcomm Snapdragon mobile platforms including SM8550, SM8650, SM8750, SM7675, SM6650, and their P/Q variants
Qualcomm compute and IoT platforms including QCS6490, QCS8550, QCS9100, QCS5430, QCS615, QCM5430, QCM6490, QCM8550, SG8275, and SXR2330P
Qualcomm connectivity firmware including WCN7850/7851/7860/7861/7880/7881, WCN6650/6750/6755/6855/6856, WCN3910/3950, QCA6391, QCA6698AQ, and QCN9011/9012/9274

Discovery Timeline

2025-09-24 - CVE CVE-2025-21476 published to NVD alongside the Qualcomm September 2025 Security Bulletin
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-21476

Vulnerability Analysis

The vulnerability resides in the code path that marshals parameters into the Trusted Virtual Machine (TVM) during handshake initialization. When a caller in the non-secure world hands off parameters to the trusted VM, the boundary code fails to properly validate the size or structure of the input before copying it into a fixed-size destination buffer. The result is a classic buffer copy without checking size of input, categorized as [CWE-120].

Because the corruption occurs during handshake with a trusted component, the attacker operates across a security boundary that is normally relied upon to isolate sensitive workloads. The attack requires local access and low privileges, but no user interaction, meaning any process able to reach the TVM interface can attempt exploitation.

Root Cause

The root cause is insufficient bounds checking on parameters supplied to the TVM handshake routine. Fixed-size internal buffers accept caller-controlled length or content data without validating that the input fits the destination. This enables overflow of adjacent memory structures used during the handshake, corrupting execution state within the trusted component.

Attack Vector

Exploitation requires local access to an affected Qualcomm-based device. A low-privileged process invokes the TVM handshake interface and supplies malformed or oversized parameters. When the handshake code copies these parameters without size validation, memory corruption occurs inside the trusted VM context. Depending on the corrupted region, the attacker may achieve elevation of privilege or compromise the isolation guarantees of the trusted environment.

No public proof-of-concept exploit or in-the-wild exploitation has been reported at the time of publication. Full technical specifics are held by Qualcomm; see the Qualcomm Security Bulletin September 2025 for vendor details.

Detection Methods for CVE-2025-21476

Indicators of Compromise

Unexpected crashes, resets, or watchdog reboots involving the trusted execution environment or hypervisor components on Qualcomm chipsets
Kernel or firmware logs referencing TVM handshake failures, aborts, or SError exceptions shortly after suspicious userspace activity
Unauthorized processes invoking low-level Qualcomm trusted service interfaces (qseecom, smcinvoke, or vendor hab/gunyah device nodes)

Detection Strategies

Monitor mobile device management (MDM) telemetry for devices running firmware predating the Qualcomm September 2025 patch level
Correlate abnormal TVM/hypervisor error signatures with process execution timelines to identify potential exploitation attempts
Use endpoint and mobile threat defense tooling to flag applications that access low-level trusted-service IOCTLs without a legitimate business need

Monitoring Recommendations

Enroll affected devices into centralized logging so kernel panics and firmware reset reasons are retained for forensic review
Track Qualcomm security bulletin patch levels across the fleet and alert when devices fall behind the September 2025 baseline
Baseline normal invocation patterns of trusted-service interfaces so anomalous callers become visible in behavioral analytics

How to Mitigate CVE-2025-21476

Immediate Actions Required

Identify all devices, modules, and OEM products that use the affected Qualcomm chipsets listed in the September 2025 bulletin
Apply firmware and Android security patches from OEMs that incorporate the Qualcomm September 2025 update as they become available
Restrict installation of untrusted applications on affected devices until patches are deployed, since local access is required for exploitation

Patch Information

Qualcomm addressed CVE-2025-21476 in the September 2025 Security Bulletin. Device manufacturers integrate the fix into their monthly firmware and Android security patch releases. Consult the Qualcomm Security Bulletin September 2025 and the corresponding OEM advisories for exact firmware versions applicable to each platform.

Workarounds

No official vendor workaround is documented; patching is the required remediation path
Reduce risk in the interim by enforcing application allow-listing and blocking sideloading on managed mobile and IoT deployments
For embedded and automotive deployments, limit physical and debug interface access to authorized personnel until updated firmware is validated and deployed