CVE Intelligence
CISA KEV Medium SSRF

CVE-2021-21973 — VMware vCenter Server and Cloud Foundation Server Side Request Forgery (SSRF) Vulnerability

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).

Published Feb 24, 2021 · Updated Oct 13, 2026 · Sources: CISA Known Exploited Vulnerabilities, NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: vmware

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

CISA KEV · Mar 7, 2022 Detection templates (Nuclei) · 1Proofs of concept on GitHub · 1
How the score was calculated
  • Confirmed exploitation (CISA KEV)+35
  • Public exploit/PoC (nuclei, github)+10
  • EPSS 88% (30-day exploitation probability)+15
  • Technical severity (medium)+3
  • Automatable exploitation (SSVC)+3

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation
Confirmed
CISA KEV, listed Mar 7, 2022
EPSS FIRST
88.01%
ahead of 100% of scored CVEs · Oct 14, 2026
Affects
Vmware
Cloud Foundation and 1 more
CVSS base
5.3
Medium · 3 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation
Active
none · proof-of-concept · active
Automatable
Yes
can an attacker script the kill-chain steps
Technical impact
Partial
partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

CISA required action CISA

Apply updates per vendor instructions.

US federal deadline: Mar 21, 2022 — passed 1669 day(s) ago

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

  1. Identify exposed assets running the affected vendor/product/version combinations (Vmware Cloud Foundation, Vmware Vcenter Server).
  2. Treat as emergency remediation: the CVE is in CISA KEV (confirmed exploitation).
  3. The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
  4. No fix documented in the sources: reduce exposure and monitor the vendor advisory.
  5. EPSS ahead of 100% of scored CVEs: prioritize it in the patch queue.
  6. Search available logs for exploit probes matching the vulnerability class (ssrf), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

VendorProductVersionsStatusSource
Vmware Cloud Foundation ≥ 4.0 and < 4.2≥ 3.0 and < 3.10.1.2 Vulnerable NIST National Vulnerability Database
Vmware Vcenter Server version 6.7-bversion 7.0-update1aversion 6.7-dversion 6.7-update1version 6.7-update1bversion 6.7-update2version 6.7-update2aversion 6.7-update2c
and 33 more version 6.7-update3version 6.7-update3aversion 6.7-update3bversion 6.7-update3fversion 6.7-update3gversion 6.7-update3jversion 7.0version 7.0-aversion 7.0-bversion 7.0-cversion 7.0-dversion 7.0-update1version 6.5-update2version 6.5version 6.5-aversion 6.5-bversion 6.5-cversion 6.5-dversion 6.5-eversion 6.5-fversion 6.5-update1dversion 6.5-update1eversion 6.5-update1gversion 6.7-aversion 6.5-update2bversion 6.5-update2cversion 6.5-update2dversion 6.5-update2gversion 6.5-update3version 6.5-update3dversion 6.5-update3fversion 6.5-update3kversion 6.7
Vulnerable NIST National Vulnerability Database

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
None

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

ScoreVersionSeverityExpl.ImpactScored by
5.3 CVSS 3.1 Medium 3.9 1.4 nvd@nist.gov via NIST National Vulnerability Database
5.3 CVSS 3.1 Medium 3.9 1.4 134c704f-9b21-4f2e-91b3-4a467353bcc0 via NIST National Vulnerability Database
5.3 CVSS 3.1 Medium — — CISA-ADP via CVE Program (cve.org) e CISA ADP
5.0 CVSS 2.0 Medium 10.0 2.9 nvd@nist.gov via NIST National Vulnerability Database
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N (score shown at the top: nvd@nist.gov)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

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

Other CVEs with this weakness →

CISA KEV details CISA

CISA lists a CVE once it has evidence of exploitation against real targets.

Listed
Mar 7, 2022
Federal deadline
Mar 21, 2022
passed 1669 day(s) ago
Ransomware use
Unknown

CISA records ransomware use only for campaigns it has confirmed, so “Unknown” means unrecorded, not ruled out. The deadline binds US federal agencies; for everyone else it is a reference date.

Public exploits, PoCs and detection templates

Public code that demonstrates or tests the flaw raises the odds of mass exploitation — and Nuclei templates help find vulnerable assets in your environment.

Detection templates (Nuclei)
Proofs of concept on GitHub

Warning: public PoCs are sometimes disguised malware. Use them only for authorized testing in an isolated environment. This portal does not host exploit code — it only points to the sources.

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 88.01%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

  • Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
  • Monitor outbound requests from the server to internal IPs and cloud metadata endpoints.
  • Hunt retroactively in logs from before Mar 7, 2022 (KEV listing): exploitation may have started earlier.
web/proxy/WAF logsnetwork IDS/IPSegress traffic

Timeline

What happened to this CVE, newest first.

  • 2026
  • SSVC assessment updated
    Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
  • Record published
    Oct 13, 2026
  • Affected products added · vmware/cloud foundation, vmware/vcenter server
    Oct 13, 2026 · NIST National Vulnerability Database
  • CVSS changed · 5.3
    Oct 13, 2026 · NIST National Vulnerability Database
  • Source status changed · → Analyzed
    Oct 13, 2026 · NIST National Vulnerability Database
  • Added to CISA KEV (detected)
    Oct 13, 2026 · CISA Known Exploited Vulnerabilities
  • Record created in this database
    Oct 13, 2026 · CISA Known Exploited Vulnerabilities
  • 2022
  • Added to CISA KEV catalog
    Mar 6, 2022 · CISA
  • 2021
  • CVE published
    Feb 24, 2021 · vmware

Source activity

Repeated readings are counted rather than listed.

  • 1× References added · Oct 13, 2026 – Oct 13, 2026
  • 1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

2 on the record

Elsewhere on this site

Vmware
every CVE for this vendor
2022-03
what else CISA listed that month
SSRF
same class
CWE-918
other pages naming this weakness

Related CVEs (same products)

  • CVE-2026-41709 ESX insufficient logging vulnerability Jul 30, 2026
  • CVE-2026-59310 Broadcom VMware vCenter Path Traversal Vulnerability KEV Jul 30, 2026
  • CVE-2026-59309 vCenter authentication-bypass vulnerability Jul 30, 2026
  • CVE-2026-47876 VMXNET3 out-of-bounds write vulnerability Jul 30, 2026
  • CVE-2026-41703 Out-of-bounds read vulnerability Jul 30, 2026
  • CVE-2026-41724 VMSA-2026-0004: VMware Cloud Foundation Operations updates address multiple vulnerabilities (CVE-2026-41722, CVE-2026-41723 and CVE-2026-41724) Jun 8, 2026

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

  • No fixed version, patch or mitigation documented.
  • No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
  • No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
  • No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2021-21973 is "VMware vCenter Server and Cloud Foundation Server Side Request Forgery (SSRF) Vulnerability", rated Medium. It affects Cloud Foundation (Vmware); versions are in the scope table. It is in CISA KEV: there is evidence of real-world exploitation. CVSS 5.3 describes technical severity. EPSS 88.01% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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