CVE-2021-21973
VMware vCenter Server and Cloud Foundation Server Side Request Forgery (SSRF) Vulnerability
Description
CVE-2021-21973 is a medium-severity server-side request forgery (ssrf) vulnerability affecting VMware vCenter Server and Cloud Foundation. VMware vCenter Server and Cloud Foundation Server contain a SSRF vulnerability due to improper validation of URLs in a vCenter Server plugin. This allows for information disclosure. CISA has added this vulnerability to its Known Exploited Vulnerabilities (KEV) catalog, confirming active exploitation in the wild. With an EPSS score of 90.51% (99.6th percentile), this vulnerability has a notable probability of exploitation.
KEV Information
CVSS Score
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:NOpen in CalculatorAffected Products
| Vendor | Product | Version |
|---|---|---|
| vmware | cloud foundation | >= 3.0, < 3.10.1.2; >= 4.0, < 4.2 |
| vmware | vcenter server | 6.5; 6.7; 7.0 |
Multiple CVSS Assessments
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
References
- https://www.vmware.com/security/advisories/VMSA-2021-0002.html(Vendor Advisory)
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-21973(US Government Resource)
Weakness Type
CWE-918: Server-Side Request Forgery (SSRF)
Server-Side Request Forgery (SSRF) occurs when a web application fetches a remote resource without validating the user-supplied URL. This allows attackers to coerce the application to send requests to an unexpected destination, even when protected by a firewall, VPN, or network access control list.
Learn more: CWE-918 — Server-Side Request Forgery (SSRF)
Impact Analysis
CVE-2021-21973 carries a CVSS 3.1 score of 5.3 (MEDIUM), indicating a moderate-severity threat. The vulnerability is exploitable over the network with low attack complexity and requires no authentication. Successful exploitation can partially compromise data confidentiality. Organizations running affected vCenter Server and Cloud Foundation deployments face significant operational risk if this vulnerability remains unpatched.
Exploit Maturity
CVE-2021-21973 is confirmed as actively exploited through its listing in the CISA Known Exploited Vulnerabilities catalog. The EPSS score of 90.51% (99.6th percentile) reflects an exceptionally high probability of exploitation. Federal agencies were required to remediate this vulnerability by 2022-03-21 per CISA's binding operational directive.
Remediation
- Apply vendor patches immediately as mandated by CISA KEV: Apply updates per vendor instructions.
- Verify that all instances of affected products (vmware cloud foundation >= 3.0, < 3.10.1.2; >= 4.0, < 4.2; vmware vcenter server 6.5; 6.7; 7.0) have been updated to patched versions.
- If immediate patching is not possible, restrict network access to affected systems using firewall rules and network segmentation to limit exposure.
- Monitor systems for indicators of compromise, including unusual process activity, unexpected network connections, and unauthorized configuration changes.
- Review security logs and conduct threat hunting to determine if the vulnerability was exploited prior to patching.
Technical Details
CVE-2021-21973 affects VMware vCenter Server and Cloud Foundation. VMware vCenter Server and Cloud Foundation Server contain a SSRF vulnerability due to improper validation of URLs in a vCenter Server plugin. This allows for information disclosure. The attack vector is network-based, meaning an attacker can exploit this vulnerability remotely without physical access to the target system. The CVSS score of 5.3 reflects a moderate vulnerability, but its inclusion in the KEV catalog confirms real-world exploitation risk.
Frequently Asked Questions
Is CVE-2021-21973 being actively exploited?
Yes. CVE-2021-21973 is listed in the CISA Known Exploited Vulnerabilities catalog, confirming active exploitation. The EPSS score of 90.51% (99.6th percentile) further indicates a very high exploitation probability.
What products are affected by CVE-2021-21973?
CVE-2021-21973 affects VMware vCenter Server and Cloud Foundation. Specifically affected products include: vmware cloud foundation (>= 3.0, < 3.10.1.2; >= 4.0, < 4.2), vmware vcenter server (6.5; 6.7; 7.0).
How do I fix CVE-2021-21973?
Apply updates per vendor instructions. Ensure all affected systems are updated to the latest patched versions. If patching is not immediately possible, implement network-level mitigations to limit exposure.
How severe is CVE-2021-21973?
CVE-2021-21973 has a CVSS 3.1 score of 5.3 (MEDIUM). While rated as medium severity, its presence in the KEV catalog confirms it is being actively exploited and should be remediated promptly.
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