FKIE_CVE-2021-26887
Vulnerability from fkie_nvd - Published: 2021-03-11 16:15 - Updated: 2026-08-19 17:17
Severity
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
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.
References
Impacted products
| Vendor | Product | Version | |
|---|---|---|---|
| microsoft | windows_10 | - | |
| microsoft | windows_10 | 20h2 | |
| microsoft | windows_10 | 1607 | |
| microsoft | windows_10 | 1803 | |
| microsoft | windows_10 | 1809 | |
| microsoft | windows_10 | 1909 | |
| microsoft | windows_10 | 2004 | |
| microsoft | windows_7 | - | |
| microsoft | windows_8.1 | - | |
| microsoft | windows_rt_8.1 | - | |
| microsoft | windows_server_2008 | - | |
| microsoft | windows_server_2008 | r2 | |
| microsoft | windows_server_2012 | - | |
| microsoft | windows_server_2012 | r2 | |
| microsoft | windows_server_2016 | - | |
| microsoft | windows_server_2016 | 20h2 | |
| microsoft | windows_server_2016 | 1909 | |
| microsoft | windows_server_2016 | 2004 | |
| microsoft | windows_server_2019 | - |
{
"affected": [
{
"affectedData": [
{
"platforms": [
"32-bit Systems",
"x64-based Systems"
],
"product": "Windows 10 Version 1507",
"vendor": "Microsoft",
"versions": [
{
"status": "affected",
"version": "-"
}
]
},
{
"platforms": [
"32-bit Systems",
"x64-based Systems"
],
"product": "Windows 10 Version 1607",
"vendor": "Microsoft",
"versions": [
{
"status": "affected",
"version": "-"
}
]
},
{
"platforms": [
"32-bit Systems",
"ARM64-based Systems",
"x64-based Systems"
],
"product": "Windows 10 Version 1803",
"vendor": "Microsoft",
"versions": [
{
"status": "affected",
"version": "-"
}
]
},
{
"platforms": [
"32-bit Systems",
"x64-based Systems"
],
"product": "Windows 10 Version 1809",
"vendor": "Microsoft",
"versions": [
{
"status": "affected",
"version": "-"
}
]
},
{
"platforms": [
"ARM64-based Systems"
],
"product": "Windows 10 Version 1809",
"vendor": "Microsoft",
"versions": [
{
"status": "affected",
"version": "-"
}
]
},
{
"platforms": [
"32-bit Systems",
"ARM64-based Systems",
"x64-based Systems"
],
"product": "Windows 10 Version 1909",
"vendor": "Microsoft",
"versions": [
{
"status": "affected",
"version": "-"
}
]
},
{
"platforms": [
"32-bit Systems",
"ARM64-based Systems",
"x64-based Systems"
],
"product": "Windows 10 Version 2004",
"vendor": "Microsoft",
"versions": [
{
"status": "affected",
"version": "-"
}
]
},
{
"platforms": [
"32-bit Systems",
"ARM64-based Systems"
],
"product": "Windows 10 Version 20H2",
"vendor": "Microsoft",
"versions": [
{
"status": "affected",
"version": "-"
}
]
},
{
"platforms": [
"32-bit Systems"
],
"product": "Windows 7",
"vendor": "Microsoft",
"versions": [
{
"status": "affected",
"version": "-"
}
]
},
{
"platforms": [
"x64-based Systems"
],
"product": "Windows 7 Service Pack 1",
"vendor": "Microsoft",
"versions": [
{
"status": "affected",
"version": "-"
}
]
},
{
"platforms": [
"32-bit Systems",
"ARM64-based Systems",
"x64-based Systems"
],
"product": "Windows 8.1",
"vendor": "Microsoft",
"versions": [
{
"status": "affected",
"version": "-"
}
]
},
{
"platforms": [
"x64-based Systems"
],
"product": "Windows Server 2008 R2 Service Pack 1",
"vendor": "Microsoft",
"versions": [
{
"status": "affected",
"version": "-"
}
]
},
{
"platforms": [
"x64-based Systems"
],
"product": "Windows Server 2008 R2 Service Pack 1 (Server Core installation)",
"vendor": "Microsoft",
"versions": [
{
"status": "affected",
"version": "-"
}
]
},
{
"platforms": [
"32-bit Systems",
"x64-based Systems"
],
"product": "Windows Server 2008 Service Pack 2",
"vendor": "Microsoft",
"versions": [
{
"status": "affected",
"version": "-"
}
]
},
{
"platforms": [
"32-bit Systems",
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],
"product": "Windows Server 2008 Service Pack 2 (Server Core installation)",
"vendor": "Microsoft",
"versions": [
{
"status": "affected",
"version": "-"
}
]
},
{
"platforms": [
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],
"product": "Windows Server 2012",
"vendor": "Microsoft",
"versions": [
{
"lessThan": "6.2.9200.23298",
"status": "affected",
"version": "6.2.9200.0",
"versionType": "custom"
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},
{
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"product": "Windows Server 2012 (Server Core installation)",
"vendor": "Microsoft",
"versions": [
{
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"status": "affected",
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},
{
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"vendor": "Microsoft",
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"vendor": "Microsoft",
"versions": [
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},
{
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"product": "Windows Server 2016",
"vendor": "Microsoft",
"versions": [
{
"status": "affected",
"version": "-"
}
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},
{
"platforms": [
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"product": "Windows Server 2016 (Server Core installation)",
"vendor": "Microsoft",
"versions": [
{
"status": "affected",
"version": "-"
}
]
},
{
"platforms": [
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],
"product": "Windows Server 2019",
"vendor": "Microsoft",
"versions": [
{
"status": "affected",
"version": "-"
}
]
},
{
"platforms": [
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],
"product": "Windows Server 2019 (Server Core installation)",
"vendor": "Microsoft",
"versions": [
{
"status": "affected",
"version": "-"
}
]
},
{
"platforms": [
"x64-based Systems"
],
"product": "Windows Server version 2004",
"vendor": "Microsoft",
"versions": [
{
"status": "affected",
"version": "-"
}
]
},
{
"platforms": [
"x64-based Systems"
],
"product": "Windows Server version 20H2",
"vendor": "Microsoft",
"versions": [
{
"status": "affected",
"version": "-"
}
]
},
{
"platforms": [
"x64-based Systems"
],
"product": "Windows Server, version 1909 (Server Core installation)",
"vendor": "Microsoft",
"versions": [
{
"status": "affected",
"version": "-"
}
]
}
],
"source": "secure@microsoft.com"
}
],
"configurations": [
{
"nodes": [
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],
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "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\u0027s personal data to a created folder.\nTo 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.\nThis 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."
},
{
"lang": "es",
"value": "Una Vulnerabilidad de Elevaci\u00f3n de Privilegios de Folder Redirection de Microsoft Windows"
}
],
"id": "CVE-2021-26887",
"lastModified": "2026-08-19T17:17:44.767",
"metrics": {
"cvssMetricV2": [
{
"acInsufInfo": false,
"baseSeverity": "MEDIUM",
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"accessVector": "LOCAL",
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},
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"source": "nvd@nist.gov",
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}
],
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"ssvcV203": [
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"options": [
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{
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{
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],
"role": "CISA Coordinator",
"timestamp": "2024-01-09T18:27:46.711163Z",
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"published": "2021-03-11T16:15:15.800",
"references": [
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{
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"sourceIdentifier": "secure@microsoft.com",
"vulnStatus": "Modified",
"weaknesses": [
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{
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"value": "CWE-59"
}
],
"source": "nvd@nist.gov",
"type": "Primary"
}
]
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
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.
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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.
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.
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