CVE-2008-4037: Windows SMB credential reflection allows remote code execution

Automated analysis

Generated by VULONE's analysis model from the NVD record, CISA KEV and EPSS data on 19 September 2026. Confidence: high.

high priorityRemote code execution with complete impact and mature public exploit code, though exploitation requires the victim to initiate an SMB connection and the affected platforms are legacy.

What it is

Windows SMB clients fail to properly authenticate server responses, letting a malicious SMB server replay a connecting user's NTLM credentials back at the client. Because the replayed credentials are accepted as valid, the attacker can execute arbitrary code on the client machine in the context of the logged-on user. The flaw is an improper authentication issue (CWE-287) and is reported as an insufficient fix for CVE-2000-0834.

Impact

An attacker controlling an SMB server gains remote code execution on the connecting Windows client with the privileges of the victim user, giving full compromise of confidentiality, integrity and availability.

Attack surface

Reached over the network via SMB: the victim must connect to an attacker-controlled or attacker-spoofed SMB server, which can be induced by a link, shortcut or name-resolution poisoning. No authentication to the attacker's server is required, but user interaction to initiate the SMB connection is typically needed.

Exploitation

Not listed in CISA KEV, but EPSS is very high (0.591, 99th percentile) and public exploit code is referenced (backrush, Exploit-DB 7125), indicating mature, widely available exploitation.

What to do

• Apply Microsoft security update MS08-068 (the vendor fix for this vulnerability) to all affected Windows versions.
• Disable or restrict outbound SMB (TCP 445/139) from clients to untrusted networks at the perimeter and host firewall.
• Enable SMB signing where feasible to prevent credential relay/reflection abuse.
• Block NetBIOS/LLMNR name resolution poisoning and restrict WebDAV/UNC path handling to reduce forced SMB connections.
• Retire unsupported platforms (Windows 2000, XP, Server 2003) that cannot receive current fixes.

Detection

• Monitor for outbound SMB connections from workstations to unexpected or external hosts, especially repeated authentication attempts.
• Alert on SMB authentication events where a client authenticates to a server and the same credentials are then used back toward the client (reflection pattern).
• Hunt for processes spawned shortly after SMB session establishment on client hosts, particularly from services or user sessions that initiated SMB traffic.
• Review logs for NTLM authentication to non-domain or newly seen SMB servers and correlate with user-reported link or shortcut clicks.

This assessment is produced automatically and is not human-reviewed. Verify against the vendor advisory before acting on it.