CVE-2021-21992Network attack vector

Authenticated service interruption via improper XML entity parsing

Published Sep 22, 2021 · Updated Aug 3, 2024

Improper XML entity parsing in VMware vCenter Server 6.5, 6.7, and 7.0 allows remote authenticated users to interrupt service. The affected vCenter Server parser processes XML entities improperly; VMware has not disclosed the parser implementation or malformed document structure. A non-administrative account with HTML5 or FLEX/Flash client access is required, including for affected Cloud Foundation releases; the advisory does not identify the interruption as a hang, crash, or reboot.

CVSS severity6.5
Medium
EPSS probability0.98%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper XML entity parsing in VMware vCenter Server 6.5, 6.7, and 7.0 allows remote authenticated users to interrupt service. The affected vCenter Server parser processes XML entities improperly; VMware has not disclosed the parser implementation or malformed document structure. A non-administrative account with HTML5 or FLEX/Flash client access is required, including for affected Cloud Foundation releases; the advisory does not identify the interruption as a hang, crash, or reboot.

The record

CVE
CVE-2021-21992
Published
Sep 22, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
T1499.004
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 22, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

6.8NIST NVDAV:N/AC:L/Au:S/C:N/I:N/A:C
6.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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