A now-resolved security vulnerability in Styra's Open Policy Agent (OPA) could have exposed New Technology LAN Manager (NTLM) hashes, potentially leading to credential leakage. If exploited, the flaw allowed attackers to capture the NTLM credentials of the OPA server’s local user account and send them to a remote server. From there, they could either crack the password or relay the authentication, according to a report by cybersecurity firm Tenable, shared with The Hacker News.

The vulnerability, identified as CVE-2024-8260 and classified as a Server Message Block (SMB) force-authentication flaw, affected both the Command Line Interface (CLI) and the Go software development kit (SDK) on Windows. The issue arose from improper input validation, enabling unauthorized access by leaking the Net-NTLMv2 hash of the logged-in user on the Windows device running OPA.

Exploiting this vulnerability required specific conditions: the victim had to initiate outbound SMB traffic over port 445, gain an initial foothold through social engineering, or run the OPA CLI using a Universal Naming Convention (UNC) path rather than a Rego rule file.

Tenable security researcher Shelly Raban explained that when a Windows machine accesses a remote share, it sends the NTLM hash of the local user to authenticate to the remote server. Attackers can capture these credentials to perform relay attacks or crack the password offline. Following the responsible disclosure in June 2024, the issue was patched in version 0.68.0, released on August 29, 2024.

Tenable emphasized the importance of securing open-source projects to avoid exposing vendors and users to potential threats. The disclosure of this vulnerability coincides with Akamai's revelation of a privilege escalation flaw (CVE-2024-43532) in Microsoft's Remote Registry Service, which also involved NTLM relay attacks.

Microsoft, in response to NTLM vulnerabilities, reiterated its commitment to replace NTLM with Kerberos in Windows 11 to enhance authentication security.