CVE-2021-31166

Microsoft HTTP Protocol Stack: Remote Code Execution

As of , CVE-2021-31166 in Microsoft HTTP Protocol Stack is on CISA's list of exploited vulnerabilities: CISA listed it on . Our patch-first group: Patch this week.

Exploited
Yes: CISA listed it on 6 April 2022
US federal deadline
27 April 202221 days after CISA listed it. US federal civilian agencies must fix it by then.
Used in ransomware campaigns
Not known to CISA
EPSS score
0.99Higher than 99% of the CVEs EPSS scores. EPSS estimates the chance of exploitation activity in the next 30 days.
EPSS when listed
0.85 on 6 April 2022EPSS on the day CISA listed it.
Public exploit
1 Metasploit module
Fix
No vendor link in CISA's entry

What CISA says to do

Apply updates per vendor instructions.

CISA's required action

What the flaw is

Microsoft HTTP Protocol Stack contains a vulnerability in http.sys that allows for remote code execution.

CISA's description

HTTP Protocol Stack Remote Code Execution Vulnerability

The CVE record's description, from microsoft

CVE published
11 May 2021
Assigned by
microsoft
CVSS
9.8 Critical (CVSS 3.1, from the CNA)
CWE-416
Use After Free
CISA SSVC, exploitation
active
CISA SSVC, automatable
yes
CISA SSVC, technical impact
total

Timeline

  1. The CVE record was published.
  2. CISA added it to its list of exploited vulnerabilities.
  3. The US federal deadline to fix it.

Public exploits

Facts from Metasploit's module list and Exploit-DB's index; we never copy exploit code.

  • Metasploit: Windows IIS HTTP Protocol Stack DOSauxiliary module, rank normal

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