CVE-2021-22017 — Vcenter Server
MEDIUMCVE-2021-22017 is a medium-severity (CVSS 5.3) vulnerability in vmware vcenter server. It is in CISA's Known Exploited Vulnerabilities catalog (added 2022-01-10) — treat it as actively exploited and patch now. No vendor fix is recorded yet; mitigation options are listed below.
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…
Exploitation Status
Actively exploited in the wild
- Confirmed by CISA's Known Exploited Vulnerabilities catalog on 2022-01-10. Federal agencies were required to remediate by 2022-01-24.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
Exploitation and automatability from CISA (KEV catalog and SSVC triage) for CVE-2021-22017.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2021-22017 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 395,249 CVEs with a current EPSS score, this one falls in the 10–50% band (highlighted). Counts from FIRST.org, log-scaled.
Description
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 Products
vcenter servervmwareResearch use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Vendor / applianceDetect
Inventory every vmware vcenter server deployment and check each version against the affected-products list above.
Remediation status
No patch has shipped for CVE-2021-22017 yet — track the vmware vcenter server advisory for a fixed release and apply the workarounds below in the meantime.
Mitigate without a patch
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands. Alongside that, restrict the management interface to trusted networks and apply the vendor's recommended configuration mitigations.
How to detect CVE-2021-22017
A community-maintained Nuclei template exists for this CVE. You can scan for it directly:
nuclei -id cve-2021-22017 -u https://target- Template
- vCenter Server - Improper Access Control
- Severity
- medium
- Impact
- Attackers can bypass proxy restrictions and access internal endpoints, potentially leading to information disclosure or further internal network compromise.
- Remediation
- Apply the latest security patches or updates provided by VMware for vCenter Server.
Template by ProjectDiscovery nuclei-templates (daffainfo), MIT licensed. View the full template. Scan only systems you are authorised to test.
Frequently Asked Questions
Is CVE-2021-22017 being exploited in your environment?
Detect and block the exploit chain at execution, on systems you cannot patch yet.