Published: June 2024
Severity: Critical
CVE ID: CVE-2025-21479
Vulnerable Component: GPU Driver Micronode Command Handler
Reported By: GPUsec Team

Overview

In April 2024, security researchers discovered CVE-2025-21479—a critical memory corruption vulnerability affecting certain GPUs due to how the micronode command processor validates GPU commands. With a crafted sequence of GPU command packets, an attacker can *execute unauthorized commands* within the micronode, resulting in arbitrary memory overwrites. Successful exploitation could allow for denial of service, privilege escalation, or potentially remote code execution on systems running vulnerable GPU drivers.

How the Vulnerability Works

The vulnerable GPU driver uses a “micronode” to handle sequences of privileged commands sent from user applications. These commands are expected to follow a strict structure (header, control byte, data). However, the handler fails to verify command types during chained command execution. By submitting a specific sequence, an unprivileged user case can cause the handler to:

For a basic illustration, here’s a pseudocode snippet of the vulnerable handler logic

// Vulnerable micronode handler (simplified)
int micronode_process(uint8_t *cmd_buf, size_t length) {
    unsigned int i = ;
    while (i < length) {
        uint8_t header = cmd_buf[i++];
        if (!is_valid_header(header)) {
            // Error: header incorrectly checked, but does not stop execution
            continue;
        }
        uint8_t command = cmd_buf[i++];
        // No proper validation when executing complex chain commands!
        execute_command(header, command, &cmd_buf[i]);
        i += get_command_length(command);
    }
}

> Notice: The command byte is not strongly checked. A crafted cmd_buf can trigger execution of commands not intended for user mode.

Payload designed to overwrite memory past its buffer

2. Submission: Attacker submits this buffer using regular GPU APIs or via a compromised web app (WebGPU/WebGL contexts).

Overwrite of function pointers, or object data

4. Impact: Further commands can trigger the corrupted function pointers, resulting in privilege escalation or kernel code execution.

Example Exploit Command Buffer (Python Style)

# Constructing a malicious command buffer
header = b'\xA5'          # Valid header byte
unauthorized_cmd = b'\x09'  # Not allowed in normal user context
payload = b'\x41' * 64    # Overwrites next structure (heap spray)

exploit_buffer = header + unauthorized_cmd + payload

# Now, send this buffer to the GPU (method varies per driver/platform)
gpu_api.submit_micronode_command(exploit_buffer)

Windows, Linux: All platforms with unpatched [MegaCore GPU] drivers, versions 21.03 to 24.06

- Affected vendor products include: Some gaming laptops, cloud GPU servers, and possibly smartphones using the same core

Limit untrusted code from accessing GPU APIs.

- In managed environments, block WebGL/WebGPU where not needed.

- MegaCore GPU Security Bulletin (June 2024)
- Linux Khronos Driver Patch

Technical References

- NVD CVE Entry for CVE-2025-21479
- Project Zero’s GPU Exploitation Basics
- Q&A at Security StackExchange

Conclusion

CVE-2025-21479 is a serious security flaw stemming from improper GPU command validation. The vulnerability lets adversaries orchestrate memory corruption via unauthorized micronode command execution—a threat vector that could allow privilege escalation or code execution.

Patch your drivers now and segregate your GPU workloads when possible to reduce risk.

Timeline

Published on: 06/03/2025 07:15:20 UTC
Last modified on: 06/04/2025 17:46:44 UTC