Threat actors are exploiting a SolarWinds Serv-U path-traversal vulnerability (CVE-2024-28995) using publicly available proof-of-concept (PoC) exploits. This high-severity flaw allows unauthenticated attackers to read arbitrary files by crafting specific HTTP GET requests, arising from insufficient validation of path traversal sequences. Impacted products include Serv-U FTP Server 15.4, Serv-U Gateway 15.4, Serv-U MFT Server 15.4, and older versions, with SolarWinds releasing a hotfix on June 5, 2024, to address the issue.
Despite the simplicity of the attacks, the activity underscores the risk posed by unpatched endpoints. Rapid7 analysts published a detailed write-up on exploiting the vulnerability, and an independent researcher released a PoC exploit and bulk scanner on GitHub. GreyNoise set up a honeypot to monitor exploitation attempts, observing both manual and automated attack strategies. Attackers used platform-specific path traversal sequences, exploiting incorrect slashes that the Serv-U system later corrects.
The most frequently targeted files include ‘/etc/passwd’ on Linux and ‘/windows/win.ini’ on Windows, aimed at escalating privileges or exploring further opportunities within the breached network. GreyNoise reports that while some attackers copy-paste exploits without testing, others, particularly from China, show persistence and adaptability. These attackers experimented with different payloads and formats for hours, adjusting their methods based on server responses.
Given the ongoing attacks, system administrators are urged to apply the available fixes immediately. The attacks highlight the critical need for vigilance and robust cybersecurity practices to mitigate such risks effectively. With thousands of potentially vulnerable instances exposed to the internet, the priority is to secure these endpoints to prevent unauthorized access and potential data breaches.
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