CVE-2021-31166: Microsoft HTTP Protocol Stack Remote Code Execution Vulnerability

Vulnerability summary

CVE-2021-31166 is a critical (CVSS 9.8) Use After Free vulnerability in Microsoft HTTP Protocol Stack. It is known to be exploited: CISA lists it, first on 06-04-2022. EPSS estimates a 99.87% chance of exploitation in the next 30 days, higher than 99.9% of scored vulnerabilities. 1 public exploit is recorded.

Timeline

1. 11-05-2021
   PublishedVulnerability first disclosed.
2. 06-04-2022
   Added to CISA KEVMicrosoft HTTP Protocol Stack Remote Code Execution Vulnerability
3. 27-04-2022
   CISA remediation dueApply updates per vendor instructions.
4. 21-10-2025
   Last modifiedVulnerability information updated.

Description

HTTP Protocol Stack Remote Code Execution Vulnerability

• CWE-416Use After FreeThe product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.