2024-07-02 00:55:07
A new critical vulnerability, identified as CVE-2024-6387, has been discovered in OpenSSH. This flaw implies a race condition in the token handler that can be exploited by attackers to gain unauthorized access or execute arbitrary code.
OpenSSH: An Overview
OpenSSH, or Open Secure Shell, is a set of secure networking utilities based on the Secure Shell (SSH) protocol, which provides a secure channel over an unsecured network. It is widely used for remote login, command execution, file transfer and tunneling services, ensuring encrypted communication between clients and servers.
Key features of OpenSSH
- Remote login: Secure login to remote systems.
- Encrypted traffic: All traffic between client and server is encrypted, preventing interception and hijacking of connections.
- Data integrity: It ensures the integrity and confidentiality of the data during transmission.
- Carrying on: Supports TCP/IP and X11 forwarding, allowing secure port browsing and forwarding sessions.
Vulnerability data
The IS vulnerability the way OpenSSH’s sshd daemon handles certain tokens lies. Specifically, a race condition occurs in the signal handling code that can be triggered under certain conditions. This race condition can lead to memory corruption, which allows an attacker to manipulate memory allocations and potentially execute arbitrary code.
The exploit scenario involves carefully crafted interactions with the sshd process, leveraging token handling code to create a state where memory allocation functions (malloc, free) can be manipulated. This manipulation could lead to malicious code execution or unauthorized access.
Widespread exposure: CVE-2024-6387
The CVE-2024-6387 vulnerability, also known as regreSSHion, has exposed a significant number of OpenSSH server instances to potential exploitation. Here are the main findings of this vulnerability:
- Widespread exposure: It is estimated that more than 14 million OpenSSH server instances may be vulnerable and exposed to the internet. These scenarios are susceptible to remote code execution (RCE), which could allow attackers to gain complete control over the affected systems.
- Gravity: The vulnerability can be exploited to achieve RCE, especially affecting systems running glibc-based versions of Linux. It is therefore a critical concern for organizations that rely on OpenSSH for secure remote communications.
- Historical context: The regreSSHion bug was named because it is a regression of a previous vulnerability (CVE-2006-5051) that was previously patched. This shows the importance of continuous monitoring and patch management in software security.
Technical analysis
The detailed technical breakdown provided by Qualys shows the steps attackers can take to exploit this vulnerability:
- Heap manipulation: Attackers can free a specific chunk of memory in a non-primary field, redirecting the pointer to the OpenSSH Global Offset Table (GOT).
- Overwrite code: By overwriting the entry for _exit() in the GOT with the shellcode address, attackers can take control of the execution flow.
- Timing strategy: The exploit relies on precise timing to interfere with memory operations, creating a situation where the attacker can control non-initialized areas of memory.
OpenSSH versions affected by CVE-2024-6387
The critical vulnerability CVE-2024-6387 affects several versions of OpenSSH, primarily those released between versions 8.5p1 and 9.7p1. This vulnerability, a race condition in the OpenSSH server-side token handler (sshd), allows remote code execution without authentication.
- Vulnerable versions: OpenSSH versions from 8.5p1 to 9.7p1.
- Previous versions: Versions prior to 4.4p1 are also vulnerable unless patched for CVE-2006-5051 and CVE-2008-4109.
- Recent vulnerability: The race condition in the OpenSSH sshd makes many systems vulnerable to potential attacks.
Potential impact of resurrection (CVE-2024-6387)
The vulnerability known as “regreSSHion,” identified as CVE-2024-6387, poses significant risks to systems running affected versions of OpenSSH. Here are the possible impacts:
- Remote Code Execution (RCE)
- nature: The most important impact of CVE-2024-6387 is the possibility of remote code execution.
- Consequence: Attackers can execute arbitrary code on affected systems, potentially gaining complete control over the server. This could lead to unauthorized access, data breaches and further exploitation.
- Elevation of privilege
- nature: The vulnerability could allow attackers to escalate their privileges on the compromised system.
- Consequence: An attacker with limited access could exploit this vulnerability to gain root or administrative privileges, greatly increasing the potential damage.
- System compromise
- nature: When exploited, the vulnerability could lead to complete compromise of the affected system.
- Consequence: This includes the possibility of installing malware, backdoors or other malicious tools, which could be used to exploit or further control the system.
- Data gap
- nature: With unauthorized access, attackers can intercept sensitive data.
- Consequence: This may result in the loss of confidential information, intellectual property and personal data, as well as financial and reputational damage.
- Service interruption
- nature: Exploiting the vulnerability could lead to disruption of the services provided by the affected systems.
- Consequence: This can impact business operations, cause downtime, and affects service availability to users and customers.
- Spreading Malware
- nature: Compromised systems can be used as a launch pad for additional attacks.
- Consequence: This could lead to the spread of malware within a network, affecting more systems and expanding the reach of the attack.
Mitigation and patches
To mitigate the risks associated with CVE-2024-6387, the following steps should be taken:
- Patch and update: Ensure that all systems running affected versions of OpenSSH are updated to the latest patch version.
- Monitoring and auditing: Regularly monitor and audit SSH access logs for unusual activity.
- Access controls: Implement strong access controls and use multi-factor authentication (MFA) to secure SSH access.
- Network partition: Use network partitioning to limit the exposure of SSH services to potential attackers.
- Best security practices: Follow best practices for securing SSH, including using strong, unique passwords and disabling root logins.
He is a recognized expert in mobile security and malware analysis. He studied Computer Science at NYU and started working as a cybersecurity analyst in 2003. He works actively as an anti-malware expert. He also worked for security companies like Kaspersky Lab. He also has a deep level of knowledge of mobile security and mobile vulnerabilities.
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