Patch first › VMware (Broadcom)
CVE-2021-21985
VMware (Broadcom) vCenter Server · Virtualization, VDI and cloud
VMware vCenter Server Improper Input Validation Vulnerability
At a glance
Exploited. Added to CISA’s catalog of exploited vulnerabilities on November 3, 2021.
Used in ransomware attacks, according to CISA.
Affected product: VMware (Broadcom) vCenter Server (category Virtualization, VDI and cloud, indicative classification). Name in CISA’s catalog: VMware vCenter Server.
What should I do?
Apply the security update from VMware (Broadcom).
Deadline set by CISA for US federal agencies: 14 days (due November 17, 2021). It only binds those agencies, but it is a useful measure of urgency.
- VMware (Broadcom) security advisories page (general page, not the advisory for this vulnerability)
- The vendor’s specific advisory is listed in the NVD references: CVE-2021-21985 on the NVD website.
Original text of the required action (CISA)
Apply updates per vendor instructions.
Timeline
- Vulnerability published Publication date (NVD)
- Exploitation confirmed Added to CISA’s KEV catalog
- CISA deadline Remediation deadline set for US federal agencies
The facts, with their sources
- Exploitation confirmed
- Yes, on November 3, 2021 Date added to the catalog of exploited vulnerabilities. Exploitation itself may have started earlier. Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
- Ransomware
- Known use Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
- Hunt for compromise
- Not requested by CISA Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
- CISA required action
- Apply the security update from VMware (Broadcom). Rewritten by this site from CISA’s original text. Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
- CISA deadline
- November 17, 2021, 14 days Set for US federal agencies: a measure of urgency, not an obligation elsewhere. Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
- Vulnerability published
- May 26, 2021 Source: National Vulnerability Database (NVD), collected September 29, 2026 at 15:00 UTC
- Product according to CISA
- VMware vCenter Server Filed by this site under “Virtualization, VDI and cloud” (indicative classification). Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
- CVSS vector
- CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Technical detail of the score: attack vector, complexity, impact. Source: National Vulnerability Database (NVD), collected September 29, 2026 at 15:00 UTC
Severity and activity
FIRST’s EPSS model. Since exploitation is already confirmed, this figure is mostly useful to compare activity. Collected Sep 29, 2026.
Description
The vSphere Client (HTML5) contains a remote code execution vulnerability due to lack of input validation in the Virtual SAN Health Check plug-in which is enabled by default in vCenter Server. 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.
Official description from the NVD, collected Sep 29, 2026. CVE® description © The MITRE Corporation.
VMware vSphere Client contains an improper input validation vulnerability in the Virtual SAN Health Check plug-in, which is enabled by default in vCenter Server, which allows for remote code execution.
Summary from CISA (KEV catalog).
CERT-FR advisories
No advisory among the latest CERT-FR publications this site follows. That does not mean there are none.
Information reused under the Open Licence 2.0 (Etalab); the date of last update is shown for each advisory. This site is neither affiliated with nor endorsed by ANSSI.
Sources for this page
- CISA KEV catalog: exploitation, date added, required action, deadline, ransomware.
- NVD (NIST): CVSS severity, publication date, description, vendor references.
- EPSS (FIRST): probability of exploitation.
- CERT-FR: advisories and alerts (in French).
- Brand and category: indicative classification by this site (method).