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Known exploited vulnerability · CISA KEV

CVE-2021-22017: VMware vCenter Server Improper Access Control

Rhttproxy as used in vCenter Server contains a vulnerability due to improper implementation of URI normalization.

CVE-2021-22017

Exploited in the wild. Fix this first.

CISA added it to the Known Exploited Vulnerabilities catalog on 2022-01-10: attackers are using it right now.

CISA KEV
Listed
Added 2022-01-10 · federal fix-by 2022-01-24
EPSS (30 days)
49%
Higher than 99% of CVEs · 2026-11-01
CVSS v3.1
5.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

What CISA says

VMware vCenter Server Improper Access Control

Apply updates per vendor instructions.

NVD description · published 2021-09-23

Rhttproxy as used in vCenter Server contains a vulnerability due to improper implementation of URI normalization. A malicious actor with network access to port 443 on vCenter Server may exploit this issue to bypass proxy leading to internal endpoints being accessed.

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How to check if you are exposed to CVE-2021-22017

  1. Find every VMware vCenter Server system you or your clients run, including ones exposed to the internet. Those come first: CISA only lists flaws attackers are already using.
  2. Compare each version with the fixed versions in the vendor advisory. Where no fix exists yet, apply the vendor’s mitigation or take the system off the internet.
  3. Run a credentialed vulnerability scan to catch the systems you missed, then check that the next scan no longer reports CVE-2021-22017.

US federal agencies had to fix this by 2022-01-24. Everyone else should treat that deadline as a guide: if it has passed, this is overdue.

Affected versions

Versions the National Vulnerability Database lists as vulnerable to CVE-2021-22017. Check the vendor advisory for the exact fixed builds before you sign anything off.

ProductVulnerable versions
VMware Vcenter Server6.7

Timeline

  1. · Published in the National Vulnerability Database
  2. · Added to CISA's Known Exploited Vulnerabilities catalog, 109 days after it was published
  3. · Fix-by date for US federal agencies, passed 1,742 days ago

Weakness type

More exploited VMware vulnerabilities

CISA lists 26 exploited VMware vulnerabilities. The closest matches:

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Sources: CISA Known Exploited Vulnerabilities catalog (version 2026.10.30); EPSS data from FIRST.org; CVSS and descriptions from the NIST National Vulnerability Database. Checked 2026-11-01. This product uses the NVD API but is not endorsed or certified by the NVD.

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