CVE-2021-26866

Exploitation

Not assessed. CISA has not published an exploitation assessment for this record, and it is not in the KEV catalog. That is an absence of assessment, not a finding of no risk.

SSVC decision

Not assessed by CISA

EPSS probability

1.15% probability of exploitation activity in the next 30 days.

EPSS percentile

Equal to or higher than the score of 66.9% of scored records. A rank, not a probability.

NVD base score

7.1 (CVSS v3.x), scored by the NVD independently of the CNA.

NVD CVSS vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H

NVD analysis status

Modified. NVD last modified this record on 2026-08-19.

Red Hat severity

No Red Hat rating. Red Hat rates the CVEs that affect its products.

Exploit-prediction scores from FIRST. Independent scoring and analysis status from the NVD. Vendor severity from Red Hat. Exploitation assessment and catalog membership from CISA.

Published

2021-03-11 15:38Z5 YR AGO

Last updated

2026-08-19 16:30Z2 MO AGO

Reserved

2021-02-08

Assigning CNA

microsoft

Record state

PUBLISHED

Severity

High (CVSS 7.1)

CNA CVSS vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H/E:U/RL:O/RC:C

Weaknesses

No CWE assigned

Data version

5.2

Document digest

e210bddddd073785d550773fc9a59b0f73e851a7646db4fbe66eacccb0b3cf8d

• msrc.microsoft.comWindows Update Service Elevation of Privilege Vulnerabilityhttps://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-26866vendor-advisorypatch
• portal.msrc.microsoft.comhttps://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26866x_refsource_MISC
• www.zerodayinitiative.comhttps://www.zerodayinitiative.com/advisories/ZDI-21-286/x_refsource_MISC