CVE-2021-21972
CRITICALCVE-2021-21972 is a critical-severity (CVSS 9.8) Path Traversal vulnerability. It is in CISA's Known Exploited Vulnerabilities catalog (added 2021-11-03) and has been used in ransomware campaigns — treat it as actively exploited and patch now. No vendor fix is recorded yet; mitigation options are listed below.
The vSphere Client (HTML5) contains a remote code execution vulnerability in a vCenter Server plugin. A malicious actor with network access to port 443 may exploit this issue to execute…
Exploitation Status
Actively exploited in the wild
- Confirmed by CISA's Known Exploited Vulnerabilities catalog on 2021-11-03 — including use in ransomware campaigns. Federal agencies were required to remediate by 2021-11-17.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA (KEV catalog and SSVC triage) for CVE-2021-21972.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2021-21972 by exploitation likelihood (EPSS) against impact (CVSS). In the shaded patch-first corner (EPSS 50%+, CVSS 7.0+).
Where this sits among everything scored
Of 395,249 CVEs with a current EPSS score, this one falls in the ≥ 90% band (highlighted). Counts from FIRST.org, log-scaled.
Description
The vSphere Client (HTML5) contains a remote code execution vulnerability in a vCenter Server plugin. A malicious actor with network access to port 443 may exploit this issue to execute commands with unrestricted privileges on the underlying operating system that hosts vCenter Server. 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
cloud foundationvmwarevcenter servervmwareResearch use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
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Detection & mitigation playbook
VulnerabilityDetect
Identify every host running the affected component and compare the installed build against the fixed version below — for source-built or distro-packaged software the version string, not a lockfile, is the source of truth (`dpkg -l`, `rpm -q`, or the binary's own `--version`).
Remediation status
No fixed release is recorded for CVE-2021-21972 yet. Track the upstream advisory, and apply the exposure-reduction steps below in the meantime.
Mitigate without a patch
Resolve every user-supplied path to its canonical form and reject anything that escapes the intended directory, and run the component under an account that has no read or write access outside the directory it legitimately serves.
How to detect CVE-2021-21972
A community-maintained Nuclei template exists for this CVE. You can scan for it directly:
nuclei -id cve-2021-21972 -u https://target- Template
- VMware vSphere Client (HTML5) - Remote Code Execution
- Severity
- critical
- Impact
- Successful exploitation of this vulnerability could allow an attacker to execute arbitrary code on the affected system.
- Remediation
- Apply the necessary security patches or updates provided by VMware to mitigate this vulnerability.
Template by ProjectDiscovery nuclei-templates (dwisiswant0), MIT licensed. View the full template. Scan only systems you are authorised to test.
Frequently Asked Questions
Is CVE-2021-21972 in your dependencies?
Find it across , including transitive dependencies.