Threat Intelligence Report: RegreSSHion Vulnerability in OpenSSH (CVE-2024-6387)

CISO Executive Summary #

Overview #

The RegreSSHion vulnerability, identified as CVE-2024-6387, is a critical remote unauthenticated code execution vulnerability in OpenSSH server versions 8.0 to 9.4. This vulnerability allows attackers to execute arbitrary code on affected systems without authentication, posing a significant risk to organizations using OpenSSH for secure communication.

Impact #

The impact of CVE-2024-6387 is severe due to its potential for remote code execution without authentication. Exploiting this vulnerability can lead to unauthorized access to sensitive data, compromise of critical systems, potential for lateral movement within a network, and disruption of services.

Mitigation #

To mitigate the risk posed by CVE-2024-6387:

1. Upgrade OpenSSH: Apply the latest patches and upgrade to a version of OpenSSH that addresses this vulnerability (9.5 or later).
2. Network Segmentation: Implement network segmentation to limit exposure of OpenSSH servers to untrusted networks.
3. Firewall Rules: Configure firewall rules to restrict access to OpenSSH servers from trusted IP addresses only.
4. Monitoring and Detection: Deploy intrusion detection and prevention systems to monitor for suspicious activity related to this vulnerability.

Engineering Breakdown #

CVE Details #

• CVE ID: CVE-2024-6387
• Severity: Critical
• CVSS Score: 9.8 (Critical)
• Vector: Network
• Access Complexity: Low
• Authentication: None

Description #

The RegreSSHion vulnerability is due to improper input validation in the OpenSSH server. Specifically, the flaw exists in the way OpenSSH handles certain network packets, which can be exploited by an attacker to execute arbitrary code on the vulnerable server. This issue affects OpenSSH versions 8.0 to 9.4, and its exploitation does not require authentication.

Technical Analysis #

Palo Alto Networks Analysis #

According to Palo Alto Networks Unit 42, the vulnerability stems from a buffer overflow in the sshd component. An attacker can send a specially crafted packet to the OpenSSH server, triggering the overflow and allowing execution of arbitrary code with the privileges of the sshd process.

Qualys Analysis #

Qualys researchers highlighted that the exploit is highly reliable and can be triggered repeatedly without crashing the target system, making it an attractive target for attackers. They also noted that the vulnerability can be exploited remotely, significantly increasing the attack surface.

Splunk Analysis #

Splunk’s analysis emphasizes the potential impact of the RegreSSHion vulnerability on critical infrastructure. They warn that compromised systems could be used to launch further attacks within an organization’s network, leading to data breaches and service disruptions.

Exploitation Details #

Proof of Concept #

A publicly released proof of concept (PoC) exploit demonstrates how CVE-2024-6387 can be exploited. Below is a high-level overview of the exploitation process:

1. Crafting the Malicious Packet: The attacker crafts a specially formatted network packet designed to trigger the buffer overflow in the sshd component of OpenSSH.
2. Sending the Packet: The malicious packet is sent to the target OpenSSH server over the network.
3. Triggering the Overflow: The vulnerable sshd component processes the packet, leading to a buffer overflow and allowing the attacker to overwrite critical memory regions.
4. Executing Arbitrary Code: The attacker’s payload is executed with the privileges of the sshd process, typically root, allowing complete control over the target system.

Below is a simplified version of the PoC code used to exploit CVE-2024-6387:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <netinet/in.h>

#define TARGET_IP "192.168.1.10"
#define TARGET_PORT 22
#define PAYLOAD "MALICIOUS_PAYLOAD_HERE"

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

    sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (sockfd < 0) {
        perror("socket");
        exit(EXIT_FAILURE);
    }

    memset(&target_addr, 0, sizeof(target_addr));
    target_addr.sin_family = AF_INET;
    target_addr.sin_addr.s_addr = inet_addr(TARGET_IP);
    target_addr.sin_port = htons(TARGET_PORT);

    if (connect(sockfd, (struct sockaddr *)&target_addr, sizeof(target_addr)) < 0) {
        perror("connect");
        close(sockfd);
        exit(EXIT_FAILURE);
    }

    send(sockfd, PAYLOAD, strlen(PAYLOAD), 0);
    close(sockfd);

    printf("Exploit packet sent to %s:%d\n", TARGET_IP, TARGET_PORT);
    return 0;
}


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