Monday, May 5, 2025
HomeExploitWindows PoC Exploit Released For The Most Critical Wormable RCE in HTTP...

Windows PoC Exploit Released For The Most Critical Wormable RCE in HTTP Protocol Stack

Published on

SIEM as a Service

Follow Us on Google News

Recently cybersecurity researchers has recently discovered a severe vulnerability in the IIS (Internet Information Services) of Windows. Though Microsoft has recently fixed this critical vulnerability in patch Tuesday released in 12 may, and it’s tracked as CVE-2021-31166.

Many security experts and security companies have claimed that this vulnerability is one of the most critical security flaws that have been detected and fixed by Microsoft this month.

HTTP Protocol Stack RCE Vulnerability

This critical flaw (CVE-2021-31166) is akin to corruption of information in the memory of the HTTP protocol stack (HTTP.sys) that is already included in all the recent versions of Windows.

- Advertisement - Google News
  • CVE ID: CVE-2021-31166
  • Assigning CNA: Microsoft
  • Released: May 11, 2021
  • CVSS: 3.0 (9.8 out of 10)

In general, this HTTP Protocol Stack is used by the Windows IIS (Internet Information Services) server, so, the security expert, Axel Souchet, who used to work for Microsoft has explained that if this server is active, then an attacker can easily send it a specially crafted packet to execute malicious code at the OS kernel level.

This security flaw is quite similar to another Microsoft vulnerability that was detected in the HTTP network stack. It was tracked as CVE-2015-1635 and detected or reported by the security experts in 2015.

Moreover, it becomes worse when Microsoft warned that this RCE vulnerability has the potential of a worm, as it can be used by the threat actors to create malware that spreads itself from server to server.

PoC for CVE-2021-31166 triggers Blue Screen of Death (BSOD)

To show the flaw in action the former Microsoft security researcher, Axel Suchet published a PoC exploit for CVE-2021-31166 (“HTTP Protocol Stack Remote Code Execution Vulnerability”).

From the above image, you can see the flaw in action, and how this critical flaw triggers the Blue Screen of Death (BSOD). Here, Axel explains that where the function has a local LIST_ENTRY, this bug happens itself in the “http!UlpParseContentCoding” and then it affix the item to it.

And here the interesting thing is that it does not NULL out the local list (LIST_ENTRY) after it moves it into the Request structure when it is done.

It means that an attacker can easily leave all the entries of the local list in a hanging state in the Request object by triggering the code path that unlocks all the entries of the local list.

Possible targets are safe from attacks

Axel Suchet claimed since the capabilities of the HTTP Protocol Stack RCE flaw are artificially limited, so, it is likely that most of the potential targets are safe from such attacks.

While this security flaw only affects the newest OS versions like Windows 10 2004 and 20H2, as well as Windows Server 2004 and 20H2, and all these versions are not yet very widespread.

Moreover, the vulnerability CVE-2021-31166 does not allow the formulation of a full-fledged worm, and it only leads to a “crash” (DoS) of unpatched Windows versions that are running the IIS server.

But, apart from all these things, the security team at Microsoft has strongly recommended all its users to install all the security updates published on an immediate basis.

Balaji
Balaji
BALAJI is an Ex-Security Researcher (Threat Research Labs) at Comodo Cybersecurity. Editor-in-Chief & Co-Founder - Cyber Security News & GBHackers On Security.

Latest articles

Gunra Ransomware’s Double‑Extortion Playbook and Global Impact

Gunra Ransomware, has surfaced as a formidable threat in April 2025, targeting Windows systems...

Hackers Exploit 21 Apps to Take Full Control of E-Commerce Servers

Cybersecurity firm Sansec has uncovered a sophisticated supply chain attack that has compromised 21...

Hackers Target HR Departments With Fake Resumes to Spread More_eggs Malware

The financially motivated threat group Venom Spider, also tracked as TA4557, has shifted its...

RomCom RAT Targets UK Organizations Through Compromised Customer Feedback Portals

The Russian-based threat group RomCom, also known as Storm-0978, Tropical Scorpius, and Void Rabisu,...

Resilience at Scale

Why Application Security is Non-Negotiable

The resilience of your digital infrastructure directly impacts your ability to scale. And yet, application security remains a critical weak link for most organizations.

Application Security is no longer just a defensive play—it’s the cornerstone of cyber resilience and sustainable growth. In this webinar, Karthik Krishnamoorthy (CTO of Indusface) and Phani Deepak Akella (VP of Marketing – Indusface), will share how AI-powered application security can help organizations build resilience by

Discussion points


Protecting at internet scale using AI and behavioral-based DDoS & bot mitigation.
Autonomously discovering external assets and remediating vulnerabilities within 72 hours, enabling secure, confident scaling.
Ensuring 100% application availability through platforms architected for failure resilience.
Eliminating silos with real-time correlation between attack surface and active threats for rapid, accurate mitigation

More like this

Windows NTLM Vulnerability (CVE-2025-24054) Actively Exploit in the Wild to Hack Systems

A critical vulnerability in Microsoft Windows, identified as CVE-2025-24054, has been actively exploited in...

Critical SUSE Linux Distro Injection Vulnerability Allow Attackers Exploits “go-git” Library

A significant security vulnerability, designated CVE-2025-21613, has been discovered in the go-git library, used...

Hackers Weaponize Security Testing By Weaponizing npm, PyPI, & Ruby Exploit Packages

Over the past year, malicious actors have been abusing OAST services for data exfiltration,...