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

Vulnerability from cvelistv5 – Published: 2021-03-11 15:42 – Updated: 2026-08-19 16:30
VLAI
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
References
Impacted products
Vendor Product Version CPE status
Microsoft Windows 10 Version 1507 Affected: -
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Microsoft Windows 10 Version 1607 Affected: -
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Microsoft Windows 10 Version 1803 Affected: -
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Microsoft Windows 10 Version 1809 Affected: -
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Microsoft Windows 10 Version 1909 Affected: -
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Microsoft Windows 10 Version 2004 Affected: -
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Microsoft Windows 10 Version 20H2 Affected: -
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Microsoft Windows 7 Affected: -
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Microsoft Windows 7 Service Pack 1 Affected: -
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Microsoft Windows 8.1 Affected: -
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Microsoft Windows Server 2008 R2 Service Pack 1 Affected: -
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Microsoft Windows Server 2008 R2 Service Pack 1 (Server Core installation) Affected: -
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Microsoft Windows Server 2008 Service Pack 2 Affected: -
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Microsoft Windows Server 2008 Service Pack 2 (Server Core installation) Affected: -
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Microsoft Windows Server 2012 Affected: 6.2.9200.0 , < 6.2.9200.23298 (custom)
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Microsoft Windows Server 2012 (Server Core installation) Affected: 6.2.9200.0 , < 6.2.9200.23298 (custom)
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Microsoft Windows Server 2012 R2 Affected: -
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Microsoft Windows Server 2012 R2 (Server Core installation) Affected: -
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Microsoft Windows Server 2016 Affected: -
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Microsoft Windows Server 2016 (Server Core installation) Affected: -
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Microsoft Windows Server 2019 Affected: -
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Microsoft Windows Server 2019 (Server Core installation) Affected: -
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Microsoft Windows Server version 2004 Affected: -
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Microsoft Windows Server version 20H2 Affected: -
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Microsoft Windows Server, version 1909 (Server Core installation) Affected: -
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Date Public
2021-03-09 16:00
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      "source": "Red Hat CSAF VEX",
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[], \"vendor\": \"Microsoft\", \"product\": \"Windows 10 Version 1909\", \"versions\": [{\"status\": \"affected\", \"version\": \"N/A\"}], \"platforms\": [\"32-bit Systems\", \"x64-based Systems\", \"ARM64-based Systems\"]}, {\"cpes\": [], \"vendor\": \"Microsoft\", \"product\": \"Windows Server, version 1909 (Server Core installation)\", \"versions\": [{\"status\": \"affected\", \"version\": \"N/A\"}], \"platforms\": [\"x64-based Systems\"]}, {\"cpes\": [], \"vendor\": \"Microsoft\", \"product\": \"Windows 10 Version 1507\", \"versions\": [{\"status\": \"affected\", \"version\": \"N/A\"}], \"platforms\": [\"32-bit Systems\", \"x64-based Systems\"]}, {\"cpes\": [], \"vendor\": \"Microsoft\", \"product\": \"Windows 10 Version 1607\", \"versions\": [{\"status\": \"affected\", \"version\": \"N/A\"}], \"platforms\": [\"32-bit Systems\", \"x64-based Systems\"]}, {\"cpes\": [], \"vendor\": \"Microsoft\", \"product\": \"Windows Server 2016\", \"versions\": [{\"status\": \"affected\", \"version\": \"N/A\"}], \"platforms\": [\"x64-based Systems\"]}, {\"cpes\": [], \"vendor\": \"Microsoft\", \"product\": \"Windows Server 2016 (Server Core installation)\", \"versions\": [{\"status\": \"affected\", \"version\": \"N/A\"}], \"platforms\": [\"x64-based Systems\"]}, {\"cpes\": [], \"vendor\": \"Microsoft\", \"product\": \"Windows 7\", \"versions\": [{\"status\": \"affected\", \"version\": \"N/A\"}], \"platforms\": [\"32-bit Systems\"]}, {\"cpes\": [], \"vendor\": \"Microsoft\", \"product\": \"Windows 7 Service Pack 1\", \"versions\": [{\"status\": \"affected\", \"version\": \"N/A\"}], \"platforms\": [\"x64-based Systems\"]}, {\"cpes\": [], \"vendor\": \"Microsoft\", \"product\": \"Windows 8.1\", \"versions\": [{\"status\": \"affected\", \"version\": \"N/A\"}], \"platforms\": [\"32-bit Systems\", \"x64-based Systems\", \"ARM64-based Systems\"]}, {\"cpes\": [], \"vendor\": \"Microsoft\", \"product\": \"Windows Server 2008 Service Pack 2\", \"versions\": [{\"status\": \"affected\", \"version\": \"N/A\"}], \"platforms\": [\"32-bit Systems\"]}, {\"cpes\": [], \"vendor\": \"Microsoft\", \"product\": \"Windows Server 2008 Service Pack 2 (Server Core installation)\", \"versions\": [{\"status\": \"affected\", \"version\": \"N/A\"}], \"platforms\": [\"32-bit Systems\", \"x64-based Systems\"]}, {\"cpes\": [], \"vendor\": \"Microsoft\", \"product\": \"Windows Server 2008  Service Pack 2\", \"versions\": [{\"status\": \"affected\", \"version\": \"N/A\"}], \"platforms\": [\"x64-based Systems\"]}, {\"cpes\": [], \"vendor\": \"Microsoft\", \"product\": \"Windows Server 2008 R2 Service Pack 1\", \"versions\": [{\"status\": \"affected\", \"version\": \"N/A\"}], \"platforms\": [\"x64-based Systems\"]}, {\"cpes\": [], \"vendor\": \"Microsoft\", \"product\": \"Windows Server 2008 R2 Service Pack 1 (Server Core installation)\", \"versions\": [{\"status\": \"affected\", \"version\": \"N/A\"}], \"platforms\": [\"x64-based Systems\"]}, {\"cpes\": [\"cpe:2.3:o:microsoft:windows_server_2012:*:*:*:*:*:*:x64:*\"], \"vendor\": \"Microsoft\", \"product\": \"Windows Server 2012\", \"versions\": [{\"status\": \"affected\", \"version\": \"6.2.0\", \"lessThan\": \"publication\", \"versionType\": \"custom\"}], \"platforms\": [\"x64-based Systems\"]}, {\"cpes\": [\"cpe:2.3:o:microsoft:windows_server_2012:*:*:*:*:*:*:x64:*\"], \"vendor\": \"Microsoft\", \"product\": \"Windows Server 2012 (Server Core installation)\", \"versions\": [{\"status\": \"affected\", \"version\": \"6.2.0\", \"lessThan\": \"publication\", \"versionType\": \"custom\"}], \"platforms\": [\"x64-based Systems\"]}, {\"cpes\": [], \"vendor\": \"Microsoft\", \"product\": \"Windows Server 2012 R2\", \"versions\": [{\"status\": \"affected\", \"version\": \"N/A\"}], \"platforms\": [\"x64-based Systems\"]}, {\"cpes\": [], \"vendor\": \"Microsoft\", \"product\": \"Windows Server 2012 R2 (Server Core installation)\", \"versions\": [{\"status\": \"affected\", \"version\": \"N/A\"}], \"platforms\": [\"x64-based Systems\"]}], \"datePublic\": \"2021-03-09T08:00:00.000Z\", \"references\": [{\"url\": \"https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26887\", \"tags\": [\"x_refsource_MISC\"]}], \"descriptions\": [{\"lang\": \"en-US\", \"value\": \"\u003cp\u003eAn 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\u0027s personal data to a created folder.\u003c/p\u003e\\n\u003cp\u003eTo 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.\u003c/p\u003e\\n\u003cp\u003eThis 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 \u003cstrong\u003eFAQ\u003c/strong\u003e section of this CVE for configuration guidance.\u003c/p\u003e\"}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en-US\", \"type\": \"Impact\", \"description\": \"Elevation of Privilege\"}]}], \"providerMetadata\": {\"orgId\": \"f38d906d-7342-40ea-92c1-6c4a2c6478c8\", \"shortName\": \"microsoft\", \"dateUpdated\": \"2023-12-29T20:09:12.476Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2021-26887\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2024-11-19T16:07:28.981Z\", \"dateReserved\": \"2021-02-08T00:00:00.000Z\", \"assignerOrgId\": \"f38d906d-7342-40ea-92c1-6c4a2c6478c8\", \"datePublished\": \"2021-03-11T15:42:16.000Z\", \"assignerShortName\": \"microsoft\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.1"
    }
  }
}



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Tags
Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

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.


Detection rules are retrieved from Rulezet.