CVE-2021-31166 Windows HTTP flaw also impacts WinRM servers
Vulnerabilities mentionedAll →
| CVE | Vulnerability | CVSS | EPSS | Flags | Affected | Exposure | Published |
|---|---|---|---|---|---|---|---|
| CVE-2021-31166 | Use-After-Free RCE in Microsoft Windows HTTP Protocol Stack (http.sys) CVE-2021-31166 is a use-after-free vulnerability (CWE-416) in the Microsoft HTTP Protocol Stack, the kernel-mode HTTP service (http.sys) used by Windows components including IIS and WinRM. A remote, unauthenticated attacker can trigger the flaw by sending specially crafted network packets to a service that listens through http.sys, and reporting indicates WinRM servers are also impacted. Successful exploitation yields remote code execution in the kernel context, with full compromise potential (high confidentiality, integrity and availability impact), consistent with the wormable classification in vendor-adjacent reporting. Affected platforms are Windows 10 versions 2004 and 20H2 and Windows Server versions 2004 and 20H2, which were the current shipping Windows versions at the May 2021 Patch Tuesday release where the fix appeared. The issue is tracked in CISA's Known Exploited Vulnerabilities catalog (added 2022-04-06) and carries a near-certain EPSS exploitation probability (~99.8%), indicating active exploitation in the wild. Do: Apply the May 2021 Patch Tuesday security updates for Windows 10 and Windows Server versions 2004 and 20H2, prioritizing internet-facing systems running IIS, WinRM, or other http.sys-based listeners. As an interim mitigation, restrict inbound access to HTTP and WinRM endpoints at the firewall. Confirm remediation by verifying the OS build includes the May 2021 cumulative update, and check the CISA KEV catalog action (apply updates per vendor instructions). | 9.8 | 100% | KEV |
| masswell over 1,000,000 vulnerable systems (tens of millions of Windows 10 2004/20H2 installs, with likely hundreds of thousands of internet-exposed servers via… |
Full article387 words · extracted from securityaffairs.com · click to collapse
The wormable CVE-2021-31166 vulnerability in the HTTP Protocol Stack of the Windows IIS server also affects WinRM on Windows 10 and Server systems.
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.
Now, the security researcher Jim DeVries reported that the issue also impacts Windows 10 and Server devices running the Windows Remote Management (WinRM) service. a component of the Windows Hardware Management feature set which also makes use of the vulnerable HTTP.sys.
Windows Remote Management (WinRM) is the Microsoft implementation of WS-Management Protocol, a standard Simple Object Access Protocol (SOAP)-based, firewall-friendly protocol that allows hardware and operating systems, from different vendors, to interoperate.
The WinRM service is enabled by default on Windows servers running versions 2004 or 20H2 for this reason it only poses a serious risk to corporate environments, DeVries explained to BleepingComputer.
I finally found time to answer my own question. WinRM *IS* vulnerable. This really expands the number of vulnerable systems, although no one would intentionally put that service on the internet.
— Jim DeVries (@JimDinMN) May 19, 2021
At the time of this writing, querying the Shodan search engine we can found more than 1,6 million Windows systems running the WinRM service are exposed online, and those which runs versions 2004 and 20H2 are vulnerable to CVE-2021-31166 exploit.
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Text extracted automatically; images, tables and formatting may be missing. Original: https://securityaffairs.com/118189/security/cve-2021-31166-windows-http-flaw.html