CyberSecBulletin
CVE-2021-41379Exploited in the wildNVD status: Analyzed

Microsoft Windows Installer Privilege Escalation

Published Updated By the CyberSecBulletin desk

CVE-2021-41379 is a high-severity improper link resolution before file access vulnerability in Windows 10 Version 1507 from Microsoft, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists version 10.0.10240.19119 as the first without the flaw, so updating Windows 10 Version 1507 to that release or later removes the exposure. CISA added it to the Known Exploited Vulnerabilities catalogue on March 3, 2022, which means attacks have been observed in the wild, including in ransomware campaigns.

Patch now

Attackers are already exploiting this vulnerability, according to CISA.

What to do

  1. Update Windows 10 Version 1507 to 10.0.10240.19119 or a later version.
  2. Update Windows 10 Version 1607 to 10.0.14393.4770 or a later version.
  3. Update Windows 10 Version 1809 to 10.0.17763.2300 or a later version.
  4. CISA's required action: Apply updates per vendor instructions.
  5. Read the advisory on msrc.microsoft.com for workarounds and exact fixed builds.

Affected products and versions

VendorProductAffected versionsFixed in
MicrosoftWindows 10 Version 150710.0.10240.0 up to, but not including, 10.0.10240.1911910.0.10240.19119
MicrosoftWindows 10 Version 160710.0.14393.0 up to, but not including, 10.0.14393.477010.0.14393.4770
MicrosoftWindows 10 Version 180910.0.17763.0 up to, but not including, 10.0.17763.2300; 10.0.0 up to, but not including, 10.0.17763.230010.0.17763.2300
MicrosoftWindows 10 Version 190910.0.0 up to, but not including, 10.0.18363.191610.0.18363.1916
MicrosoftWindows 10 Version 200410.0.0 up to, but not including, 10.0.19041.134810.0.19041.1348
MicrosoftWindows 10 Version 20H210.0.0 up to, but not including, 10.0.19042.134810.0.19042.1348
MicrosoftWindows 10 Version 21H110.0.0 up to, but not including, 10.0.19043.134810.0.19043.1348
MicrosoftWindows 11 version 21H210.0.22000.0 up to, but not including, 10.0.22000.31810.0.22000.318
MicrosoftWindows 76.1.0 up to, but not including, 6.1.7601.257696.1.7601.25769
MicrosoftWindows 7 Service Pack 16.1.0 up to, but not including, 6.1.7601.257696.1.7601.25769
MicrosoftWindows 8.16.3.0 up to, but not including, 6.3.9600.201746.3.9600.20174
MicrosoftWindows Server 2008 R2 Service Pack 16.1.7601.0 up to, but not including, 6.1.7601.257696.1.7601.25769
MicrosoftWindows Server 2008 R2 Service Pack 1 (Server Core installation)6.1.7601.0 up to, but not including, 6.1.7601.257696.1.7601.25769
MicrosoftWindows Server 2008 Service Pack 26.0.6003.0 up to, but not including, 6.0.6003.212826.0.6003.21282
MicrosoftWindows Server 2008 Service Pack 2 (Server Core installation)6.0.6003.0 up to, but not including, 6.0.6003.212826.0.6003.21282
MicrosoftWindows Server 20126.2.9200.0 up to, but not including, 6.2.9200.235176.2.9200.23517
MicrosoftWindows Server 2012 (Server Core installation)6.2.9200.0 up to, but not including, 6.2.9200.235176.2.9200.23517
MicrosoftWindows Server 2012 R26.3.9600.0 up to, but not including, 6.3.9600.201746.3.9600.20174
MicrosoftWindows Server 2012 R2 (Server Core installation)6.3.9600.0 up to, but not including, 6.3.9600.201746.3.9600.20174
MicrosoftWindows Server 201610.0.14393.0 up to, but not including, 10.0.14393.477010.0.14393.4770
MicrosoftWindows Server 2016 (Server Core installation)10.0.14393.0 up to, but not including, 10.0.14393.477010.0.14393.4770
MicrosoftWindows Server 201910.0.17763.0 up to, but not including, 10.0.17763.230010.0.17763.2300
MicrosoftWindows Server 2019 (Server Core installation)10.0.17763.0 up to, but not including, 10.0.17763.230010.0.17763.2300
MicrosoftWindows Server 202210.0.20348.0 up to, but not including, 10.0.20348.35010.0.20348.350
MicrosoftWindows Server version 200410.0.0 up to, but not including, 10.0.19041.134810.0.19041.1348

Version data comes from the organisation that assigned the CVE; 13 further products are omitted here. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
LocalThe attacker needs local access or must trick a user into running something.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
LowA basic user account is enough.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.

Scoring systemScoreSeverityScored by
CVSS 3.15.5MediumCNA (microsoft.com)
CVSS 3.17.8HighNVD
CVSS 2.04.6MediumNVD

Official description

Windows Installer Elevation of Privilege Vulnerability

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Improper Link Resolution Before File Access

The product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource.

How developers prevent this class of flaw

  • Follow the principle of least privilege when assigning access rights to entities in a software system. Denying access to a file can prevent an attacker from replacing that file with a link to a sensitive file. Ensure good compartmentalization in the system to provide protected areas that can be trusted.

More Improper Link Resolution Before File Access vulnerabilities (CWE-59)

Timeline

  1. CVE record published.
  2. Added to CISA's Known Exploited Vulnerabilities catalogue.
  3. Deadline for US federal agencies to remediate, set by CISA.
  4. CISA published its SSVC assessment (exploitation: active, automatable: no, technical impact: total).
  5. Record last changed materially (score, affected products, status or references).

References

Third-party and government advisories

Other vulnerabilities in Windows 10 Version 1507

All Windows 10 Version 1507 vulnerabilities

Recent Improper Link Resolution Before File Access vulnerabilities

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