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CVE-2021-26887

HIGHCVSS 7.8/10EPSS 0.92%

Last modified

CVE-2021-26887 is a high-severity vulnerability rated 7.8/10 on the CVSS scale. <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 another user's personal data to a created folder.</p> <p>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. EPSS estimates a 0.92% chance of exploitation in the next 30 days.

Description

<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 another user's personal data to a created folder.</p> <p>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.</p> <p>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 <strong>FAQ</strong> section of this CVE for configuration guidance.</p>

Metrics

CVSS 3.1
7.8/10

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

EPSS Probability
0.92%

55.7th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

VendorProductVersionsUpdate
MicrosoftWindows 10All versions—
MicrosoftWindows 1020h2—
MicrosoftWindows 101607—
MicrosoftWindows 101803—
MicrosoftWindows 101809—
MicrosoftWindows 101909—
MicrosoftWindows 102004—
MicrosoftWindows 7All versionsSp1
MicrosoftWindows 8.1All versions—
MicrosoftWindows Rt 8.1All versions—
MicrosoftWindows Server 2008All versionsSp2
MicrosoftWindows Server 2008r2Sp1
MicrosoftWindows Server 2012All versions—
MicrosoftWindows Server 2012r2—
MicrosoftWindows Server 2016All versions—
MicrosoftWindows Server 201620h2—
MicrosoftWindows Server 20161909—
MicrosoftWindows Server 20162004—
MicrosoftWindows Server 2019All versions—

References

Timeline

Published
Last Modified
Status
Modified

Frequently Asked Questions

What is CVE-2021-26887?
<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 another user's personal data to a created folder.</p> <p>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.</p> <p>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 <strong>FAQ</strong> section of this CVE for configuration guidance.</p>
How severe is CVE-2021-26887?
CVE-2021-26887 has a CVSS score of 7.8/10 (HIGH severity). The EPSS model estimates a 0.92% probability of exploitation in the next 30 days.
How do I fix CVE-2021-26887?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-26887?

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Source: NVD / NIST