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.
From the CISA KEV catalogue version 2026.11.06, with Cybergen analysis. Updated 6 Nov 2026.
Should You Worry?
- CISA confirmed exploitation in the wild and added it to the Known Exploited Vulnerabilities catalogue on 10 Jan 2022.
- Rated Medium severity (CVSS 5.3, scored by CISA).
- This product type is often exposed to the internet, which is where attackers scan for it first.
- It has been in the catalogue for 1,761 days. Systems still unpatched now have almost certainly been scanned for it.
What It Is
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.
Affected Versions
| Product | Versions |
|---|---|
| VMware vCenter Server, VMware Cloud Foundation | VMware vCenter Server(6.7 before 6.7 U3o and 6.5 before 6.5 U3q) and VMware Cloud Foundation 3.x before 3.10.2.2 |
From the public CVE record, as supplied by the vendor. Always confirm against the vendor advisory.
What To Do Now
- 1
Find it
Search your asset inventory and external attack surface for VMware vCenter Server. Include cloud images, appliances and anything a supplier runs for you.
Attack Surface Management - 2
- 3
Hunt for compromise
If an affected system was reachable before you patched, assume it may have been hit. Check logs, new accounts, web shells and outbound connections from the date of exposure.
Incident Response - 4
Prove it is fixed
Rescan or test the system after patching. Upgrades that fail silently and forgotten secondary instances are common.
Penetration Testing
Vendor Advisories
The Compliance Clock
General guidance, not legal advice. Your obligations depend on your sector, scope and jurisdiction.
Not Sure If You Are Exposed?
Our attack surface and vulnerability teams can check your internet-facing estate for CVE-2021-22017 and every other exploited flaw on the list.