What is the CVSS score of CVE-2021-21973?

CVE-2021-21973 has a CVSS 3.1 base score of 5.3 (Medium). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N. EPSS exploitation probability: 88.0%.

Is there a public PoC exploit available for CVE-2021-21973?

Yes, a public proof-of-concept exploit is available for CVE-2021-21973. Prioritise patching immediately. EPSS: 88.0%.

Vcenter Server CVE-2021-21973

MEDIUM

Server-Side Request Forgery (SSRF) (CWE-918)

2021-02-24 security@vmware.com

Information Disclosure SSRF VMware Cloud Foundation Vcenter Server

5.3

CVSS 3.1 · NVD

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Vulnerability Assessment

Weakness	CWE CWE-918 OWASP Top 10:2025 A01:2025 - Broken Access Control ASVS 5.0 V4 - API and Web Service URL allowlisting, SSRF prevention MITRE ATT&CK 2 techniques across 2 tactics: Initial Access, Credential Access The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. Sign in to read
Impact	CVSS score of 5.3 (MEDIUM). Attack characteristics: network attack vector, low complexity, no privileges required, no user interaction not required.
Exploit ScenarioDerived	A remote attacker could make the server perform requests to unintended internal or external resources by sending crafted requests to the affected application. No authentication is required to exploit this vulnerability.

This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).

Exploited in the wild (CISA KEV) No patch listed yet 88.0% exploitation probability (EPSS)

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AnalysisAI

The vSphere Client (HTML5) contains an SSRF (Server Side Request Forgery) vulnerability due to improper validation of URLs in a vCenter Server plugin. Rated medium severity (CVSS 5.3), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

RemediationAI

No vendor patch is available at time of analysis. Monitor vendor advisories for updates. Validate and allowlist destination URLs, block requests to internal networks, use network segmentation.

Affects your stack

Find out whether the stacks and servers you run are on an affected version.

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

This vulnerability is classified as Server-Side Request Forgery (SSRF) (CWE-918), which allows attackers to make the server perform requests to unintended internal or external resources. 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). Affected products include: Vmware Cloud Foundation, Vmware Vcenter Server. Version information: before 7.0.

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

NVD PRIMARY 5.3 MEDIUM

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

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

Low

Integrity

None

Availability

None

Lifecycle Timeline

Added to CISA KEV

Jul 14, 2026 - 04:22 CISA

CVE Published

Feb 24, 2021 - 17:15 nvd

MEDIUM 5.3

DescriptionNVD

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).

Threat Intelligence Overview

EPSS Score

88.0%

Top 0% exploitable

Exploit

POC

Public exploit code exists

Data Quality

2 sources

Confidence: Low

NVD

CVE.org

CISA KEV

EPSS POC (1)

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue

Severity MEDIUM

CISA KEV Yes

Public POC Yes

EPSS 88.0%

Patch available No

Active threat Yes

Deciding rule

MEDIUM severity (CVSS 4.0-6.9)

What every action level means

Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.

Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.

This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.

This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.

Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived

Immediate

Exploitation· derived

Active

System Exposure· derived

Open

Automatable· derived

Yes

Human Impact· derived

High

Priority Score

184

Low Medium High Critical

KEV: +50

EPSS: +88

CVSS: +26

PoC: +20

Weaponized: 0

Threat intel: 0

Gov advisory: 0

Attack Technique

Server-Side Request Forgery HIGH

Server-Side Request Forgery exploits applications that fetch remote resources based on user-supplied URLs.

Information Disclosure MEDIUM

Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.

Affected Products (CPE)NVD

cpe:2.3:a:vmware:cloud_foundation:*:*:*:*:*:*:*:*

cpe:2.3:a:vmware:vcenter_server:6.5:-:*:*:*:*:*:*

cpe:2.3:a:vmware:vcenter_server:6.5:a:*:*:*:*:*:*

cpe:2.3:a:vmware:vcenter_server:6.5:b:*:*:*:*:*:*

cpe:2.3:a:vmware:vcenter_server:6.5:c:*:*:*:*:*:*

cpe:2.3:a:vmware:vcenter_server:6.5:d:*:*:*:*:*:*

cpe:2.3:a:vmware:vcenter_server:6.5:e:*:*:*:*:*:*

cpe:2.3:a:vmware:vcenter_server:6.5:f:*:*:*:*:*:*

cpe:2.3:a:vmware:vcenter_server:6.5:update1d:*:*:*:*:*:*

cpe:2.3:a:vmware:vcenter_server:6.5:update1e:*:*:*:*:*:*

cpe:2.3:a:vmware:vcenter_server:6.5:update1g:*:*:*:*:*:*

cpe:2.3:a:vmware:vcenter_server:6.5:update2:*:*:*:*:*:*

cpe:2.3:a:vmware:vcenter_server:6.5:update2b:*:*:*:*:*:*

cpe:2.3:a:vmware:vcenter_server:6.5:update2c:*:*:*:*:*:*

cpe:2.3:a:vmware:vcenter_server:6.5:update2d:*:*:*:*:*:*

cpe:2.3:a:vmware:vcenter_server:6.5:update2g:*:*:*:*:*:*

cpe:2.3:a:vmware:vcenter_server:6.5:update3:*:*:*:*:*:*

cpe:2.3:a:vmware:vcenter_server:6.5:update3d:*:*:*:*:*:*

cpe:2.3:a:vmware:vcenter_server:6.5:update3f:*:*:*:*:*:*

+ 23 more

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References

Advisories & patches

ADVISORY https://www.vmware.com/security/advisories/VMSA-2021-0002.html REF https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-21973

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