CVE-2021-21991

Administrator escalation via session token handling

Published Sep 22, 2021 · Updated Aug 3, 2024

Local privilege escalation in VMware vCenter Server 7.x before 7.0 U2c allows remote authenticated users to gain Administrator access via session-token handling. The vCenter Server improperly handles session tokens, permitting a non-administrative account on the vCenter host to obtain Administrator privileges in the HTML5 vSphere Client or FLEX Web Client. Exploitation requires existing non-administrative host access; the resulting privilege increase can expose and alter vCenter-managed resources.

CVSS severity7.8
High
EPSS probability0.32%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Local privilege escalation in VMware vCenter Server 7.x before 7.0 U2c allows remote authenticated users to gain Administrator access via session-token handling. The vCenter Server improperly handles session tokens, permitting a non-administrative account on the vCenter host to obtain Administrator privileges in the HTML5 vSphere Client or FLEX Web Client. Exploitation requires existing non-administrative host access; the resulting privilege increase can expose and alter vCenter-managed resources.

The record

CVE
CVE-2021-21991
Published
Sep 22, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
T1068
Attack vector
local
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 vectorlocal
Required privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

4.6NVDAV:L/AC:L/Au:N/C:P/I:P/A:P
7.8NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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.

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No observations available

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

Weakness, pattern, technique

T1068Exploitation for Privilege Escalation

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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