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Exploited vulnerability · CISA KEV

Is CVE-2021-31166 exploited? Yes: in CISA KEV since 6 Apr 2022

Gociux · Microsoft HTTP Protocol Stack · data: CISA KEV, CVE record, FIRST EPSS

Yes. CVE-2021-31166, Microsoft HTTP Protocol Stack Remote Code Execution Vulnerability, is being exploited in the wild. CISA added it to its Known Exploited Vulnerabilities catalog on 6 Apr 2022, 330 days after it was published. It affects Microsoft HTTP Protocol Stack. If you run it, CISA's required action is: Apply updates per vendor instructions.

exploitedYesCISA KEV · 6 Apr 2022
ransomwareNot knownno confirmed use
EPSStop 1%among the most likely CVEs to be exploited
severity9.8CVSS 3.1 · critical
US federal due27 Apr 2022BOD 22-01 deadline

What it is

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

VendorMicrosoft (391 exploited CVEs in KEV)
ProductHTTP Protocol Stack
VulnerabilityMicrosoft HTTP Protocol Stack Remote Code Execution Vulnerability
WeaknessCWE-416
Published11 May 2021
Added to KEV6 Apr 2022
Reported by (CNA)microsoft

What to do

  1. Check whether you run it. Look for HTTP Protocol Stack in your asset inventory, including appliances and cloud images. Stack check lists every exploited Microsoft CVE at once.
  2. Apply the fix. Apply updates per vendor instructions.
  3. If you can't patch today, take the affected service off the internet or restrict who can reach it, and check its logs for signs of compromise since 11 May 2021.
  4. Get told next time. Email alerts when CISA adds a CVE for Microsoft.

References

Questions

Is CVE-2021-31166 being exploited?

Yes. CISA added CVE-2021-31166 to the Known Exploited Vulnerabilities catalog on 6 Apr 2022, which means there is reliable evidence of exploitation in the wild.

Is CVE-2021-31166 used in ransomware attacks?

CISA does not list known ransomware use for it. That can change, and exploitation alone is reason to fix it first.

How do I fix CVE-2021-31166?

Apply updates per vendor instructions. Check Microsoft's advisory for the fixed versions, and if you can't patch quickly, restrict access to the affected HTTP Protocol Stack and watch it for signs of compromise.

Sources: CISA KEV (exploitation, ransomware use, required action, due date), the CVE record (publication date, CVSS, CNA), NVD and FIRST EPSS (live score). More: all KEV additions in April 2022 · Microsoft scorecard · act-now radar.

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