CriticalCVE-2021-22005

    VMware vCenter Server File Upload Vulnerability (CVE-2021-22005)

    Published In CISA KEV since Sources: SingCERT, CVE.org

    What is affected, what to do

    The vCenter Server contains an arbitrary file upload vulnerability in the Analytics service. A malicious actor with network access to port 443 on vCenter Server may exploit this issue to execute code on vCenter Server by uploading a specially crafted file.

    The vulnerability is being actively exploited; treat it as a priority. CISA lists it as used in ransomware campaigns. Update cloud_foundation to version 5.0. Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • VMware vCenter Server, VMware Cloud Foundation eq VMware vCenter Server(7.x before 7.0 U2c and 6.7 before 6.7 U3o) and VMware Cloud Foundation (4.x before 4.3 and 3.x before 3.10..VMware vCenter Server(7.x before 7.0 U2c and 6.7 before 6.7 U3o) and VMware Cloud Foundation (4.x before 4.3 and 3.x before 3.10

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    Metrics

    9.8

    Priority

    XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

    Source: NVD, CVSS v3

    9.8

    CVSS v3

    Severity Critical on the scale from 0 to 10.

    Source: SingCERT, CVE.org

    —

    EPSS score

    No value is available for this vulnerability.

    Show all metrics
    Severity
    Critical
    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    254.00 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

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    actively exploited
    XIEM Effective CVSS

    XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.

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    9.8 Methodology
    CVSS v3

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    9.8
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    Actively exploited
    Published
    In CISA KEV since

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    CISA assessment (SSVC)
    Exploitation: active · automatable · Technical impact: total
    Source: CISA Vulnrichment, as of 29 January 2025
    CWE

    CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.

    Read in glossary
    CWE-22

    Response and mitigation

    Why act now?

    Prioritisation rationale

    This flaw delivers unauthenticated remote code execution against the default HTTPS management interface — any internet-exposed or broadly reachable vCenter should be treated as compromised until patch state and forensics prove otherwise. Exploitation likelihood sits at the very top of the spectrum, with continuous mass scanning for /analytics/* since 2021. CISA explicitly flags the CVE as used in ransomware campaigns; vCenter is a prime pivot because owning it yields direct control of every ESXi host and the full VM estate, including backup appliances. For any NIS2/KRITIS environment this is a P1 regardless of claimed "internal only" posture — a single phished endpoint is enough to reach it laterally.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Upgrade vCenter Server to a patched build per VMSA-2021-0020 (vCenter 7.0 U2c / 7.0 U2d, 6.7 U3o, 6.5 U3q or later — confirm exact build in the vendor advisory). Patch Cloud Foundation 3.x/4.x via the matching BOM update.
      • If patching is not immediately feasible, apply VMware workaround KB85717 (edit the endpoint entries in /etc/vmware-analytics/*.properties and the vsphere-ui service properties, restart Analytics and vsphere-ui services). Validate with a curl against /analytics/telemetry/ph/api/hyper/send — it must return HTTP 404.
      • Remove the vCenter management interface (TCP/443, TCP/5480) from every network segment that is not an admin jump host / PAW. Allow access only from dedicated admin VLANs via firewall ACL; terminate any internet exposure immediately.
      • Run a compromise assessment before patching: inspect file timestamps under /usr/lib/vmware-vsphere-ui/server/work/ and /tmp/unmig*, look for foreign JSP files inside Tomcat work directories, and grep vmware-analytics logs for POSTs against Analytics endpoints. Anything suspicious → full IR workflow, not just a patch.
      • Rotate service and SSO administrator credentials (administrator@vsphere.local, vpxuser, AD integration accounts) and reissue vCenter certificates and SAML signing keys unless exploitation can be ruled out.

    2. Runbook step 2

      Mitigation layers

      • Network segmentation: place vCenter in a management VLAN behind an explicit-allowlist firewall. Inbound only TCP/443 and TCP/5480 from admin jump hosts; outbound restricted to vendor update URLs, NTP, DNS, SIEM, LDAP/KDC. No east-west reachability from workload networks.
      • WAF / reverse proxy in front of vCenter: block /analytics/telemetry/ph/api/hyper/send, UI upload endpoints, and generic multipart POSTs carrying .jsp, .war or archive payloads. Normalise HTTP methods and cap request body size.
      • IPS/IDS: enable the Suricata/Snort rules shipped for VMSA-2021-0020 (ET-Open and vendor signatures), particularly Analytics-service file-upload and web-shell content signatures aimed at vCenter.
      • Endpoint hardening of the vCenter appliance (Photon OS): enable auditd (watches on /usr/lib/vmware-vsphere-ui/server/work, /tmp, /storage/log/vmware/analytics), require key-based SSH from a bastion only, disable interactive shell for service users.
      • IAM / least privilege: enforce MFA for all vsphere.local admins, keep break-glass accounts offline. No Domain Admin membership for vCenter service accounts. Root usage only through PAM-logged sudo sessions.
      • Backup posture: patched appliances still carry attacker persistence if they were already compromised. Isolate snapshots/backups from the suspected window and restore only in a lab.

    3. Runbook step 3

      Detection rules

      • vCenter web access logs (/var/log/vmware/vsphere-ui/logs/localhost_access.*.log and Analytics logs): POSTs to /analytics/telemetry/ph/api/hyper/send or /analytics/ceip/sdk/.. with non-standard User-Agent or unusual Content-Length. Sigma shape: selection: cs-uri-stem|contains: '/analytics/telemetry/ph/api/hyper/send' + cs-method: POST.
      • Filesystem monitoring (auditd): new .jsp/.class files appearing under /usr/lib/vmware-vsphere-ui/server/work/ or other writable Tomcat work directories. Example watch: -w /usr/lib/vmware-vsphere-ui/server/work -p wa -k vcenter_webshell.
      • Process ancestry: Java processes (vsphere-ui, vmware-analytics) spawning sh, bash, python, nc, curl, wget, chmod. KQL shape: DeviceProcessEvents | where InitiatingProcessFileName in~ ("java") and FileName in~ ("sh","bash","python","nc","curl","wget").
      • Network telemetry (Zeek/Suricata): outbound connections from the vCenter IP to internet hosts, especially reverse-shell-typical ports (4444, 1337, 8443 to non-VMware ASNs) or TOR/HTTP beacons. vCenter should only talk to defined repo and licensing endpoints.
      • Account anomalies: new local OS users, SSH key additions in /root/.ssh/authorized_keys, SSO logins from unexpected source IPs. Correlate with /var/log/audit/audit.log USER_AUTH events outside the admin VLAN range.

    Detection rules

    No NEOSEC detection rule is available for this vulnerability yet.

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

    Read in glossary
    Actively exploited: treat the vulnerability as a priority in vulnerability handling under Art. 21(2)(e) NIS2. If it is exploited in your environment, check the reporting obligation under Art. 23 (early warning within 24 hours).
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

    Read in glossary
    Since 11.09.2026, manufacturers of affected products with digital elements must report actively exploited vulnerabilities under Art. 14 CRA, with an early warning within 24 hours via ENISA's single reporting platform.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    Description

    The vCenter Server contains an arbitrary file upload vulnerability in the Analytics service. A malicious actor with network access to port 443 on vCenter Server may exploit this issue to execute code on vCenter Server by uploading a specially crafted file.

    Source: CSA/SingCERT, NVD (NIST), cvelistv5, CISA KEV Catalog

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    Affected versionsFixed in
    —VMware vCenter Server, VMware Cloud Foundation
    • VMware vCenter Server(7.x before 7.0 U2c and 6.7 before 6.7 U3o) and VMware Cloud Foundation (4.x before 4.3 and 3.x before 3.10
    • —
    vmwarecloud_foundation
    • 3.0 – < 5.0
    • 5.0
    vmwarevcenter_server
    • 7.0
    • 6.5
    • 6.7
    • —
    • —
    • —

    Vendors and products

    Weakness classes (CWE)

    • CWE-22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

      Base

      The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.

      Entry at MITRE CWE-22

    Public exploit references

    Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.

    Public exploit references
    CISA KEV CatalogCISA Known Exploited Vulnerability (opens in a new tab)cisa.govactively exploited
    Packet StormVMware vCenter Server Analytics CEIP Service File Upload (opens in a new tab)packetstormsecurity.comPoC (publicly reported)reported, not verified—

    References & sources

    • vmware.comsecurity/advisories/VMSA-2021-0020.htmlx_refsource_MISC, Patch, Vendor advisory
    • packetstormsecurity.comfiles/164439/VMware-vCenter-Server-Analytics-CEIP-Service-File-…x_refsource_MISC, Exploit, Third-party advisory, Vulnerability database
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2021-22005government-resource, US government resource
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