CVE-2021-34484: Microsoft Windows User Profile Service Privilege Escalation Vulnerability

Is it exploited?

Yes. CISA added it to the Known Exploited Vulnerabilities catalog on 31 Mar 2022, 231 days after the CVE record was published.

How likely is exploitation in the next 30 days?

21.8%

EPSS score, percentile 97.6 of all scored records

How severe?

7.8 High

CVSS v3.1 base score, given by the CNA

What should I do?

CISA deadline 21 Apr 2022. Apply updates per vendor instructions.

Advisories and patches (1)

Which versions are affected?

Affected

• from 10.0.10240.0 to before 10.0.10240.19022
• from 10.0.14393.0 to before 10.0.14393.4583
• from 10.0.17763.0 to before 10.0.17763.2114
• from 10.0.0 to before 10.0.17763.2114
• from 10.0.0 to before 10.0.18363.1734
• from 10.0.0 to before 10.0.19041.1165

and 14 more in the table below

Versions by product

Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of 28 Oct 2026; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of 28 Oct 2026; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.

What to do

CISA due date for this action: 21 April 2022.

Advisories and patches

• Windows User Profile Service Elevation of Privilege Vulnerability (Vendor advisory, Patch)

Linked from CISA's catalog entry

• https://nvd.nist.gov/vuln/detail/CVE-2021-34484

Affected products and versions

As listed in the CVE record.

Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.

About this vulnerability

Microsoft Windows User Profile Service contains an unspecified vulnerability that allows for privilege escalation.

Summary: CISA's KEV catalog, as of 28 Oct 2026.

• CISA added CVE-2021-34484 to its Known Exploited Vulnerabilities (KEV) catalog on 31 Mar 2022.
• CISA's ransomware flag for this entry is "Unknown": no evidence of ransomware use in the catalog, which is not proof of none.
• The due date CISA sets for the required action is 21 Apr 2022.
• The CVE record was published on 12 Aug 2021, 231 days before it was added to KEV.
• The CVE record carries a CVSS v3.1 base score of 7.8 (High), given by its CNA.
• FIRST's EPSS model puts the probability of exploitation in the next 30 days at 21.8% (percentile 97.6), as of 28 Oct 2026.
• CISA's SSVC assessment in the CVE record: exploitation active, automatable no, technical impact total.

Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of 28 Oct 2026; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of 28 Oct 2026. About the data.

Description

Windows User Profile Service Elevation of Privilege Vulnerability

Windows User Profile Service Elevation of Privilege Vulnerability

Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.

Weakness

• CWE-269

CWE and CAPEC are maintained by MITRE; the entries are those named in the CVE record and the KEV entry.

Timeline

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