CVE-2022-33223: Transient Denial of Service in Modems due to Null Pointer Dereference when Processing Incoming Packets with HTTP Chunked Encoding

Recently, a new Common Vulnerabilities and Exposures (CVE) identifier CVE-2022-33223 has been disclosed. This vulnerability belongs to the category of Denial of Service (DoS) attacks, more specifically, Transient Denial of Service (TDoS). The vulnerability can be exploited by causing a null pointer dereference while processing incoming packets with HTTP chunked encoding in certain modems. In this blog post, we will cover the details of this vulnerability, including the code snippet responsible for the issue, original references, and the exploit details. By doing so, we aim to create awareness and promote discussions around safeguards against such vulnerabilities.

Description

HTTP chunked encoding or "chunked transfer encoding" is a data streaming mechanism used to send data over the Internet without knowing its total length beforehand. This technique breaks data into smaller chunks, which can be dynamically processed and received on-the-fly.

The vulnerability lies in the modem's handling mechanism of HTTP chunked encoding. The modem does not validate the data properly, and may access null memory (unavailable or uninitialized) under certain conditions. This ultimately leads to a crash or an unresponsive state in the modem, causing a transient denial of service.

Here's a small code snippet of the modem's handling mechanism, showcasing where the null pointer dereference occurs:

void process_packet(http_packet_t *packet) {
  // ...

  if (http_chunked_data(packet->payload)) { // Check if the incoming data is using HTTP chunked encoding
    http_chunked_parser_t *parser = http_chunked_parser_new(); // Initialize the HTTP chunked parser

    // Process the packet payload using the HTTP chunked parser
    // (Null pointer dereference vulnerability)
    http_chunked_parser_process(parser, packet->payload);

    // ...
  }

  // ...
}

The following links provide more information about the CVE-2022-33223 vulnerability

1. MITRE's CVE List
2. NVD - NIST Vulnerability Database

Exploit Details

As of now, there are no known exploits available in the public domain for this vulnerability. However, an attacker with sufficient knowledge about HTTP chunked encoding and the modem's data handling mechanism could potentially create a tailored malicious payload to trigger the null pointer dereference, consequently causing a transient denial of service in the modem.

In order to exploit the vulnerability, the attacker would need to craft HTTP requests with carefully crafted invalid chunked encoding headers. While processing these incoming packets, the modem would access invalid memory causing the crash or an unresponsive state.

Conclusion

CVE-2022-33223 is a security vulnerability that can lead to transient denial-of-service attacks in certain modems due to null pointer dereference while processing incoming packets with HTTP chunked encoding. It is crucial for modem manufacturers and software developers to be aware of this vulnerability and take preventive measures to mitigate the risks associated with it. Network administrators and users are encouraged to stay updated on security patches and follow best practices to protect their systems from vulnerabilities like CVE-2022-33223.

Timeline

Published on: 04/13/2023 07:15:00 UTC
Last modified on: 04/21/2023 03:49:00 UTC