Pierluigi Paganini
November 25, 2024
Zyxel warns that a ransomware gang has been observed exploiting a recently patched command injection vulnerability, tracked as CVE-2024-42057, in its firewalls for initial compromise.
Remote, unauthenticated attackers could exploit the flaw to execute OS commands on vulnerable devices.
According to the advisory, the attack is only possible if the device is configured to use User-Based-PSK authentication and has a valid user with a username longer than 28 characters.
“A command injection vulnerability in the IPSec VPN feature of some firewall versions could allow an unauthenticated attacker to execute some OS commands on an affected device by sending a crafted username to the vulnerable device.” reads the advisory published by the vendor. “Note that this attack could be successful only if the device was configured in User-Based-PSK authentication mode and a valid user with a long username exceeding 28 characters exists.”
The vendor addressed these vulnerabilities with the release of firmware version 5.39 for ATP, USG FLEX, and USG FLEX 50(W)/USG20(W)-VPN series.
Zyxel’s EMEA team has reported that threat actors are targeting vulnerable Zyxel security appliances. The company urges users to update admin and user account passwords for enhanced protection.
“The Zyxel EMEA team has been tracking the recent activity of threat actors targeting Zyxel security appliances that were previously subject to vulnerabilities. Since then, admin passwords have not been changed. Users are advised to update ALL administrators and ALL User accounts for optimal protection.” reads the update published by the company. “Based on our investigation, the threat actors were able to steal valid credentials information from previous vulnerabilities and such credentials were not changed, allowing them to now create SSL VPN tunnels with temporary users, such as “SUPPOR87”, “SUPPOR817” or “VPN”, and modifying the security policies to provide them with access to the device and network.”
Cybersecurity firm Sekoia recently detailed a series of attacks carried out by the Helldown ransomware gang.
“All of this evidence strongly suggests that Zyxel firewalls have been targeted by Helldown. Details about post-compromise activities indicate that, in at least one intrusion, the attacker’s tactics align with typical ransomware methods.” reads the report published by Zyxel. “Compromising firewalls or VPN gateways is a common entry technique for ransomware groups, as it provides a foothold to an organisation’s systems through equipment that is often poorly-monitored and offers access to critical resources”
Users should upgrade to the patched firmware immediately, the company also recommends temporarily disabling remote access to vulnerable firewalls.
Follow me on Twitter: @securityaffairs and Facebook and Mastodon
(SecurityAffairs – hacking, firewalls)
