VMware vCenter Server and Cloud Foundation Server Side Request Forgery (SSRF)
CVE-2021-21973 is a medium-severity server-side request forgery vulnerability in VMware vCenter Server, with a CVSS 3.1 base score of 5.3 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected VMware vCenter Server versions: 7.x before 7.0 U1c; 6.7 before 6.7 U3l; 6.5 before 6.5 U3n. The record does not name a fixed version, so check the vendor advisory. CISA added it to the Known Exploited Vulnerabilities catalogue on March 7, 2022, which means attacks have been observed in the wild.
Attackers are already exploiting this vulnerability, according to CISA.
What to do
- Update Cloud Foundation to 3.10.1.2 or 4.2, whichever matches your release line, or a later version.
- CISA's required action: Apply updates per vendor instructions.
- Read the advisory on vmware.com for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| VMware vCenter Server | VMware vCenter Server | 7.x before 7.0 U1c; 6.7 before 6.7 U3l; 6.5 before 6.5 U3n | Not stated |
| VMware Cloud Foundation | VMware Cloud Foundation | 4.x before 4.2; 3.x before 3.10.1.2 | Not stated |
| VMware | Cloud Foundation | 3.0 up to, but not including, 3.10.1.2; 4.0 up to, but not including, 4.2 | 3.10.1.2, 4.2 |
| VMware | Vcenter Server | 6.5; 6.7; 7.0 | Not stated |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- LowSome restricted data can be read.
- Integrity
- NoneNothing can be modified.
- Availability
- NoneAvailability is not affected.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 5.3 | Medium | NVD |
| CVSS 3.1 | 5.3 | Medium | CISA (ADP) |
| CVSS 2.0 | 5.0 | Medium | NVD |
Official description
The vSphere Client (HTML5) contains an SSRF (Server Side Request Forgery) vulnerability due to improper validation of URLs in a vCenter Server plugin. A malicious actor with network access to port 443 may exploit this issue by sending a POST request to vCenter Server plugin leading to information disclosure. This affects: VMware vCenter Server (7.x before 7.0 U1c, 6.7 before 6.7 U3l and 6.5 before 6.5 U3n) and VMware Cloud Foundation (4.x before 4.2 and 3.x before 3.10.1.2).
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Server-Side Request Forgery
The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination.
How developers prevent this class of flaw
- If there is a known list of applications, IP, hostname, and/or domains to which the product is allowed to communicate, then use allowlists to ensure that outgoing requests are restricted to these known entities. The allowlists could be in the application code or possibly enforced by firewalls or network segmentation.
- If the product is expected to be able to connect to arbitrary IP addresses or domains, consider using a denylist that includes private network addresses, internal domain names, etc. The denylist could be in the application code or possibly enforced by firewalls or network segmentation.
Timeline
- CVE record published.
- Added to CISA's Known Exploited Vulnerabilities catalogue.
- Deadline for US federal agencies to remediate, set by CISA.
- CISA published its SSVC assessment (exploitation: active, automatable: yes, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Third-party and government advisories
- cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-21973US Government Resource
Other vulnerabilities in VMware vCenter Server
- 9.8 Critical severity
- 9.8 Critical severity
- 7.8 High severity
- 9.8 Critical severity
- 9.8 Critical severity
- 7.2 High severity
Recent Server-Side Request Forgery vulnerabilities
- 9.8 Critical severity
- 7.2 High severity
Adminer Server-Side Request Forgery Exploited
- 9.8 Critical severity
- 7.5 High severity
- 5.5 Medium severity
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