Expert released PoC exploit code for Windows CVE-2021-31166 bug

Play ransomware Microsoft Windows DOS-to-NT path conversion process to achieve rootkit-like capabilities

A security researcher has published a working proof-of-concept exploit code for a wormable Windows IIS server vulnerability tracked as CVE-2021-31166.

Microsoft Patch Tuesday for May 2021 security updates addressed 55 vulnerabilities in Microsoft including a critical HTTP Protocol Stack Remote Code Execution vulnerability tracked as CVE-2021-31166. The flaw could be exploited by an unauthenticated attacker by sending a specially crafted packet to a targeted server utilizing the HTTP Protocol Stack (http.sys) to process packets.

This stack is used by the Windows built-in IIS server, which means that it could be easily exploited if the server is enabled. The flaw is wormable and affects different versions of Windows 10, Windows Server 2004 and Windows Server 20H2.

The security researcher Axel Souchet has published over the weekend a proof-of-concept exploit code for the wormable flaw that impacted Windows IIS.

The PoC exploit code allows to crash an unpatched Windows system running an IIS server, it does not implement worming capabilities.

Anyway attackers could start triggering the vulnerability in the wild, the PoC code could be improved to be actively exploited.

The public availability of the PoC exploit code is another good reason to apply Microsoft Patch Tuesday for May 2021 security updates as soon as possible.

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Pierluigi Paganini

(SecurityAffairs – hacking, RCE)

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Pierluigi Paganini

Pierluigi Paganini is member of the ENISA (European Union Agency for Network and Information Security) Threat Landscape Stakeholder Group and Cyber G7 Group, he is also a Security Evangelist, Security Analyst and Freelance Writer. Editor-in-Chief at "Cyber Defense Magazine", Pierluigi is a cyber security expert with over 20 years experience in the field, he is Certified Ethical Hacker at EC Council in London. The passion for writing and a strong belief that security is founded on sharing and awareness led Pierluigi to find the security blog "Security Affairs" recently named a Top National Security Resource for US. Pierluigi is a member of the "The Hacker News" team and he is a writer for some major publications in the field such as Cyber War Zone, ICTTF, Infosec Island, Infosec Institute, The Hacker News Magazine and for many other Security magazines. Author of the Books "The Deep Dark Web" and “Digital Virtual Currency and Bitcoin”.