CVE-2025-37750 SMB Client Use-After-Free Vulnerability

CVE-2025-37750 is a use-after-free vulnerability affecting the SMB client, specifically during decryption with multichannel. While specific details are scarce, the nature of a use-after-free vulnerability in a network protocol client suggests a potential for remote code execution if an attacker can control the SMB server response. Microsoft has released a security update to address this vulnerability. This vulnerability poses a significant risk to systems acting as SMB clients, as a compromised SMB server or a man-in-the-middle attacker could potentially exploit this flaw.

Attack Chain

Due to the limited information available, the following attack chain is inferred based on the nature of the vulnerability and typical SMB client interactions:

1. An attacker compromises or controls an SMB server.
2. A client initiates an SMB connection to the malicious server.
3. The server sends a response requiring multichannel negotiation.
4. The client attempts to negotiate multichannel and starts decryption.
5. The server sends a specially crafted response during decryption, triggering the use-after-free condition within the SMB client.
6. The vulnerability is triggered and allows the attacker to corrupt memory.
7. The attacker leverages the memory corruption to achieve code execution on the client machine.
8. The attacker gains control of the client system.

Impact

Successful exploitation of CVE-2025-37750 allows a malicious SMB server or man-in-the-middle attacker to execute arbitrary code on the client machine. This could lead to complete system compromise, including data theft, malware installation, and lateral movement within the network. The lack of specific details makes quantifying the exact impact difficult, but the potential for remote code execution warrants immediate attention.

Recommendation

• Apply the security update released by Microsoft to patch CVE-2025-37750.
• Monitor SMB client connections for unusual patterns or connections to untrusted servers using network connection logs (product: windows, category: network_connection).
• Deploy the provided Sigma rule to detect suspicious processes spawned after SMB client activity.