CVE-2021-26887

HIGHNVD 7.87.8—
EchelonGraph scoreMEDIUM confidence

Score 7.8 from GitHub Security Advisory (severity: HIGH) published 2022-05-24. NVD baseline CVSS 7.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
7.8
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 1%CVSS: 7.8Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

An elevation of privilege vulnerability exists in Microsoft Windows when Folder redirection has been enabled via Group Policy. When folder redirection file server is co-located with Terminal server, an attacker who successfully exploited the vulnerability would be able to begin redirecting another user's personal data to a created folder. To exploit the vulnerability, an attacker can create a new folder under the Folder Redirection root path and create a junction on a newly created User folder. When the new user logs in, Folder Redirection would start redirecting to the folder and copying personal data. This elevation of privilege vulnerability can only be addressed by reconfiguring Folder Redirection with Offline files and restricting permissions, and NOT via a security update for affected Windows Servers. See the FAQ section of this CVE for configuration guidance.

CVSS v3
7.8
EG Score
7.8(medium)
EG Risk
35(Track)
EG Risk 35/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity78% × 45%
Exploitation1% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS
56.6%
KEV
Not listed

Published

March 11, 2021

Last Modified

February 24, 2026

References (2)

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

All Vendor Advisories

(1)

Every vendor that published an advisory referencing this CVE — pulled from our cve_vendor_advisories aggregation. Click any row for the vendor's original advisory page.

Data Freshness Timeline

(refreshed 13× in last 7d / 47× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-23 14:16 UTCEPSS rescore
  2. 2026-07-23 01:58 UTCEG score recompute
  3. 2026-07-22 22:45 UTCEG score recompute
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  71. 2026-05-26 19:53 UTCVendor advisory
  72. 2026-05-26 19:53 UTCGHSA enrichment
  73. 2026-05-26 13:42 UTCEPSS rescore
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Frequently asked(5)

What is CVE-2021-26887?
CVE-2021-26887 is a high vulnerability published on March 11, 2021. <p>An elevation of privilege vulnerability exists in Microsoft Windows when Folder redirection has been enabled via Group Policy. When folder redirection file server is co-located with Terminal server, an attacker who successfully exploited the vulnerability would be able to begin redirecting…
When was CVE-2021-26887 disclosed?
CVE-2021-26887 was first published in the National Vulnerability Database on March 11, 2021, with the most recent update on February 24, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-26887 actively exploited?
CVE-2021-26887 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 56.6% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2021-26887?
CVE-2021-26887 has a CVSS v3 base score of 7.8 (NVD).
How do I remediate CVE-2021-26887?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-26887, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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