July 8, 2024by Cybersixgill

CVE-204-6387 Poses Risk to Organizations Relying on OpenSSH’s Server (sshd)

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CVE-2024-6387 is a critical vulnerability discovered in OpenSSH's server (sshd) that poses a significant risk to organizations relying on this widely used remote access and secure file transfer solution. This vulnerability, caused by a signal handler race condition, can result in a denial-of-service (DoS) attack or even allow threat actors to execute arbitrary code with the privileges of the sshd process. 

While there is currently no specific information about threat actors targeting this vulnerability, organizations must take immediate action to mitigate the risk and protect their systems. This overview provides an in-depth analysis of CVE-2024-6387, including the targeted systems and potential impact, as well as steps organizations should take to mitigate the risk and safeguard their infrastructure. By following these recommendations and staying informed about updates from the OpenSSH project, organizations can effectively address this critical vulnerability and enhance their overall security posture.


CVE-2024-6387 is a signal handler race condition vulnerability found in OpenSSH's server (sshd). This vulnerability occurs when a client fails to authenticate within the LoginGraceTime seconds, triggering sshd's SIGALRM handler asynchronously. The issue lies in the fact that this signal handler calls various functions that are not async-signal-safe, such as syslog().

At present, there is no known information regarding any specific targeted systems or organizations affected by CVE-2024-6387. However, it is important to note that OpenSSH is a widely used and popular SSH server implementation, making it potentially vulnerable to this exploit.

The potential impact of this vulnerability is significant. With a DVE score of 8.45, which indicates a high chance of exploitation, it is crucial to take this CVE seriously. If successfully exploited, an attacker could potentially gain unauthorized access to the affected system, compromising sensitive data, executing arbitrary code, or even causing a denial of service.

As for the threat actors involved, there is currently no information available regarding any specific individuals or groups targeting CVE-2024-6387. However, given the severity of the vulnerability and the potential impact it can have, it is reasonable to assume that skilled and motivated attackers may attempt to exploit this vulnerability.

To mitigate the risk associated with CVE-2024-6387, organizations should consider the following steps:

  1. Update OpenSSH: Ensure that the affected systems are running the latest version of OpenSSH. The OpenSSH project regularly releases security patches and updates to address vulnerabilities. By keeping the software up to date, organizations can protect themselves against known exploits.

  2. Monitor for suspicious activity: Implement robust monitoring and logging mechanisms to detect any unauthorized access attempts or unusual behavior. This can help identify potential exploitation of the vulnerability and allow for timely response and mitigation.

  3. Harden SSH configurations: Review and strengthen the SSH server configurations to minimize the attack surface. This includes disabling unnecessary features, enforcing strong authentication methods, and implementing access controls to limit exposure.

  4. Implement network segmentation: Isolate critical systems and sensitive data by implementing network segmentation. This can help contain the impact of a potential breach and limit lateral movement within the network.

  5. Educate users: Raise awareness among employees and system administrators about the risks associated with this vulnerability. Provide training on secure SSH practices, such as using strong passwords, enabling two-factor authentication, and avoiding suspicious links or attachments.

It is important to note that these mitigation steps are general recommendations and may need to be tailored to the specific environment and infrastructure of each organization. Regularly monitoring security advisories and staying informed about any updates or patches related to CVE-2024-6387 is crucial to maintaining a secure system.


CVE-2024-6387 - Taken from Cybersixgill’s proprietary vulnerability intelligence (DVE) Introduction

“Keep an eye on vulnerabilities“ from blog_medium, published on January 5th, 2023 by winterink

“Microsoft Windows 2000 Workstation in mixed-mode domain may ignore domain account lockout restriction due to flaw in NTLM authentication“ from advisory_carnegiemellon, published on October 13rd, 2022 by Carnegie Mellon

“Microsoft Internet Explorer (IE) permits modification of URL displayed in address bar“ from advisory_carnegiemellon, published on October 13rd, 2022 by Carnegie Mellon

This article was created using Cybersixgill IQ, our generative AI capability that supports teams with instant report writing, simplifies complex threat data and provides 24/7 assistance, transforming cybersecurity for every industry and every individual, at every level.

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