MEDIUM · CVSS 5.3 CISA Known Exploited Vulnerability

CVE-2021-22017

VMware vCenter Server Improper Access Control

VMware vCenter Server

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.

CVSS

5.3

MEDIUM

EPSS

49.2%

30-day exploitation

Ransomware groups

recorded exploiting

Published

23 Sep 2021

NVD

Exploitation status

CISA Known Exploited Vulnerabilities

Listed by CISA on 10 January 2022. US federal agencies were required to remediate it by 24 January 2022.

EPSS — exploitation probability

FIRST puts the probability of exploitation activity in the next 30 days at 49.2%, which is higher than 98.9% of all scored vulnerabilities. EPSS is a forecast of activity, not a measure of severity, and it is rescored daily.

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

Frequently asked questions

Is CVE-2021-22017 being exploited by ransomware groups?

No ransomware group in this database is currently recorded as exploiting CVE-2021-22017.

What does CVE-2021-22017 affect?

CVE-2021-22017 affects VMware vCenter Server. 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.

How severe is CVE-2021-22017?

CVE-2021-22017 is rated MEDIUM with a CVSS base score of 5.3. EPSS puts the probability of exploitation in the next 30 days at 49.2%, higher than 98.9% of all scored vulnerabilities. It is listed in the CISA Known Exploited Vulnerabilities catalog, with a federal remediation deadline of 24 January 2022.

How should organisations respond to CVE-2021-22017?

Apply the vendor patch for VMware vCenter Server as the first priority, and treat any internet-facing instance as the most urgent. Because this vulnerability is associated with ransomware activity, also review whether the affected systems were reachable before patching, rather than assuming that patching alone closes the incident.