Vulnerability-Lookup

MSRC_CVE-2021-26887

Vulnerability from csaf_microsoft - Published: 2021-03-09 08:00 - Updated: 2021-03-15 07:00

Summary

Microsoft Windows Folder Redirection Elevation of Privilege Vulnerability

Severity

Important

Notes

Additional Resources: To determine the support lifecycle for your software, see the Microsoft Support Lifecycle: https://support.microsoft.com/lifecycle

Disclaimer: The information provided in the Microsoft Knowledge Base is provided \"as is\" without warranty of any kind. Microsoft disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Microsoft Corporation or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply.

Customer Action: Required. The vulnerability documented by this CVE requires customer action to resolve.

CVE-2021-26887

7.8 (High)


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

Affected products

Fixed 40 products

Product	Identifier	Version	Remediation
Unresolved product id: 9312		—
Unresolved product id: 9318		—
Unresolved product id: 9344		—
Unresolved product id: 10047		—
Unresolved product id: 10048		—
Unresolved product id: 10049		—
Unresolved product id: 10051		—
Unresolved product id: 10287		—
Windows Server 2012 6.2.9200.23298 Windows Server 2012		6.2.9200.23298
Windows Server 2012 (Server Core installation) 6.2.9200.23298 Windows Server 2012 (Server Core installation)		6.2.9200.23298
Unresolved product id: 10481		—
Unresolved product id: 10482		—
Unresolved product id: 10483		—
Unresolved product id: 10484		—
Unresolved product id: 10543		—
Unresolved product id: 10729		—
Unresolved product id: 10735		—
Unresolved product id: 10816		—
Unresolved product id: 10852		—
Unresolved product id: 10853		—
Unresolved product id: 10855		—
Unresolved product id: 11497		—
Unresolved product id: 11498		—
Unresolved product id: 11563		—
Unresolved product id: 11568		—
Unresolved product id: 11569		—
Unresolved product id: 11570		—
Unresolved product id: 11571		—
Unresolved product id: 11572		—
Unresolved product id: 11712		—
Unresolved product id: 11713		—
Unresolved product id: 11714		—
Unresolved product id: 11715		—
Unresolved product id: 11766		—
Unresolved product id: 11767		—
Unresolved product id: 11768		—
Unresolved product id: 11769		—
Unresolved product id: 11801		—
Unresolved product id: 11802		—
Unresolved product id: 11803		—

Known affected 40 products

Product	Version	Remediation
Unresolved product id: 1	—
Unresolved product id: 2	—
Unresolved product id: 3	—
Unresolved product id: 4	—
Unresolved product id: 5	—
Unresolved product id: 6	—
Unresolved product id: 7	—
Unresolved product id: 8	—
Unresolved product id: 9	—
Unresolved product id: 10	—
Unresolved product id: 11	—
Unresolved product id: 12	—
Unresolved product id: 13	—
Unresolved product id: 14	—
Unresolved product id: 15	—
Unresolved product id: 16	—
Unresolved product id: 17	—
Unresolved product id: 18	—
Unresolved product id: 19	—
Unresolved product id: 20	—
Unresolved product id: 21	—
Unresolved product id: 22	—
Unresolved product id: 23	—
Unresolved product id: 24	—
Unresolved product id: 25	—
Unresolved product id: 26	—
Unresolved product id: 27	—
Unresolved product id: 28	—
Unresolved product id: 29	—
Unresolved product id: 30	—
Windows Server 2012 (Server Core installation) <6.2.9200.23298 Windows Server 2012 (Server Core installation)	<6.2.9200.23298	Vendor Fix fix Vendor Fix fix
Windows Server 2012 <6.2.9200.23298 Windows Server 2012	<6.2.9200.23298	Vendor Fix fix Vendor Fix fix
Unresolved product id: 33	—
Unresolved product id: 34	—
Unresolved product id: 35	—
Unresolved product id: 36	—
Unresolved product id: 37	—
Unresolved product id: 38	—
Unresolved product id: 39	—
Unresolved product id: 40	—

Threats

Impact Elevation of Privilege

Exploit Status Publicly Disclosed:No;Exploited:No;Latest Software Release:Exploitation Less Likely;Older Software Release:Exploitation Less Likely

References

7 references

URL	Category
https://msrc.microsoft.com/update-guide/vulnerabi…	self
https://msrc.microsoft.com/csaf/advisories/2021/m…	self
https://www.microsoft.com/en-us/msrc/exploitabili…	external
https://support.microsoft.com/lifecycle	external
https://www.first.org/cvss	external
https://msrc.microsoft.com/update-guide/vulnerabi…	self
https://msrc.microsoft.com/csaf/advisories/2021/m…	self

Acknowledgments

somaro

JSON

To clipboard

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CVE-2021-26887 (GCVE-0-2021-26887)

Vulnerability from cvelistv5 – Published: 2021-03-11 15:42 – Updated: 2026-08-19 16:30

Title

Microsoft Windows Folder Redirection Elevation of Privilege Vulnerability

Summary

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.

Severity

7.8 (High)


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

SSVC

Exploitation: none Automatable: no Technical Impact: total

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2024-01-09 18:27 UTC

CWE

Elevation of Privilege

Assigner

microsoft mitre root Scorecard

References

2 references

URL	Tags
https://msrc.microsoft.com/update-guide/vulnerabi…	vendor-advisorypatch
https://portal.msrc.microsoft.com/en-US/security-…	x_refsource_MISCx_transferred

Impacted products

25 products

Vendor	Product	Version
Microsoft	Windows 10 Version 1507	Affected: -
Microsoft	Windows 10 Version 1607	Affected: -
Microsoft	Windows 10 Version 1803	Affected: -
Microsoft	Windows 10 Version 1809	Affected: -
Microsoft	Windows 10 Version 1909	Affected: -
Microsoft	Windows 10 Version 2004	Affected: -
Microsoft	Windows 10 Version 20H2	Affected: -
Microsoft	Windows 7	Affected: -
Microsoft	Windows 7 Service Pack 1	Affected: -
Microsoft	Windows 8.1	Affected: -
Microsoft	Windows Server 2008 R2 Service Pack 1	Affected: -
Microsoft	Windows Server 2008 R2 Service Pack 1 (Server Core installation)	Affected: -
Microsoft	Windows Server 2008 Service Pack 2	Affected: -
Microsoft	Windows Server 2008 Service Pack 2 (Server Core installation)	Affected: -
Microsoft	Windows Server 2012	Affected: 6.2.9200.0 , < 6.2.9200.23298 (custom)
Microsoft	Windows Server 2012 (Server Core installation)	Affected: 6.2.9200.0 , < 6.2.9200.23298 (custom)
Microsoft	Windows Server 2012 R2	Affected: -
Microsoft	Windows Server 2012 R2 (Server Core installation)	Affected: -
Microsoft	Windows Server 2016	Affected: -
Microsoft	Windows Server 2016 (Server Core installation)	Affected: -
Microsoft	Windows Server 2019	Affected: -
Microsoft	Windows Server 2019 (Server Core installation)	Affected: -
Microsoft	Windows Server version 2004	Affected: -
Microsoft	Windows Server version 20H2	Affected: -
Microsoft	Windows Server, version 1909 (Server Core installation)	Affected: -

Date Public

2021-03-09 16:00

Show details on NVD website

JSON

To clipboard

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        }
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        "shortName": "microsoft"
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          "tags": [
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          "url": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-26887"
        }
      ],
      "title": "Microsoft Windows Folder Redirection Elevation of Privilege Vulnerability"
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    "datePublished": "2021-03-11T15:42:16.000Z",
    "dateReserved": "2021-02-08T00:00:00.000Z",
    "dateUpdated": "2026-08-19T16:30:31.969Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.

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MSRC_CVE-2021-26887

CVE-2021-26887 (GCVE-0-2021-26887)

Tags

Sightings

Nomenclature

Related by attack behaviour