CVE-2021-26866: microsoft windows_10 Link Following
CVSS: 7.1v3.1HighModified
Published 11-03-2021Last modified 19-08-2026
Vulnerability summary
CVE-2021-26866 is a high (CVSS 7.1) Link Following vulnerability in microsoft windows_10. EPSS estimates a 1.16% chance of exploitation in the next 30 days, higher than 66.7% of scored vulnerabilities.
CVSS score
7.1/10
010
High · v3.1 (CVE.org)EPSS score
1.16%
0%100%
Low · +0.01 pp in 30 daysKEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded
Timeline
- 11-03-2021PublishedVulnerability first disclosed.
- 19-08-2026Last modifiedVulnerability information updated.
Description
Windows Update Service Elevation of Privilege Vulnerability
CVSS metrics
3 scores · 2 sources · 2 versionsHigh 7.1Preferred score · CVE.org (CNA)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H/E:U/RL:O/RC:CSourcesAll 2 agree
- NVDNIST7.1HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H
Low 3.6Preferred score · NVD (NIST)
AV:L/AC:L/Au:N/C:N/I:P/A:PSourcesSingle source
EPSS trend
Probability
1.16%
Chance of exploitation in the next 30 days
Percentile
67%
Versus all other CVEs
30-day change
+0.01 pp
From 1.15% on 21-09-2026
21-09-202621-10-2026
EPSS score1.16%
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Microsoft15 products
- windows_10na | 20h2 | 1607 | 1803 | 1809 | 1909 | 2004
- windows 10 version 1507≥ 10.0.10240.0, < 10.0.10240.18874
- windows 10 version 1607≥ 10.0.14393.0, < 10.0.14393.4283
- windows 10 version 1803≥ 10.0.0, < 10.0.17134.2087
- windows 10 version 1809≥ 10.0.17763.0, < 10.0.17763.1817 | ≥ 10.0.0, < 10.0.17763.1817
1 vendor · 15 products
References
3 links
- portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26866X Refsource MISCX TransferredPatchVendor Advisory
- www.zerodayinitiative.com/advisories/ZDI-21-286/X Refsource MISCX TransferredThird Party AdvisoryVDB Entry