CyberSecBulletin
CVE-2026-41088NVD status: Modified

Windows 10 Version 21H2: External Control of File Name or Path

Published Updated By the CyberSecBulletin desk

CVE-2026-41088 is a high-severity external control of file name or path vulnerability in Windows 10 Version 21H2 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 10.0.19044.7291 as the first without the flaw, so updating Windows 10 Version 21H2 to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.32% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Windows 10 Version 21H2 to 10.0.19044.7291 or a later version.
  2. Update Windows 10 Version 22H2 to 10.0.19045.7417 or a later version.
  3. Update Windows 11 version 23H2 to 10.0.22631.7079 or 10.0.22631.7219, whichever matches your release line, or a later version.
  4. Read the advisory on msrc.microsoft.com for workarounds and exact fixed builds.

Affected products and versions

VendorProductAffected versionsFixed in
MicrosoftWindows 10 Version 21H210.0.19044.0 up to, but not including, 10.0.19044.729110.0.19044.7291
MicrosoftWindows 10 Version 22H210.0.19045.0 up to, but not including, 10.0.19045.741710.0.19045.7417
MicrosoftWindows 11 version 23H210.0.22631.0 up to, but not including, 10.0.22631.7079; 10.0.22631.0 up to, but not including, 10.0.22631.721910.0.22631.7079, 10.0.22631.7219
MicrosoftWindows 11 Version 24H210.0.26100.0 up to, but not including, 10.0.26100.845710.0.26100.8457
MicrosoftWindows 11 Version 25H210.0.26200.0 up to, but not including, 10.0.26200.845710.0.26200.8457
MicrosoftWindows 11 version 26H110.0.28000.0 up to, but not including, 10.0.28000.211310.0.28000.2113
MicrosoftWindows Server 202210.0.20348.0 up to, but not including, 10.0.20348.513910.0.20348.5139
MicrosoftWindows Server 2022, 23H2 Edition (Server Core installation)10.0.25398.0 up to, but not including, 10.0.25398.233010.0.25398.2330
MicrosoftWindows Server 202510.0.26100.0 up to, but not including, 10.0.26100.3286010.0.26100.32860
MicrosoftWindows Server 2025 (Server Core installation)10.0.26100.0 up to, but not including, 10.0.26100.3286010.0.26100.32860
MicrosoftWindows 10 21h2before 10.0.19044.729110.0.19044.7291
MicrosoftWindows 10 22h2before 10.0.19045.729110.0.19045.7291
MicrosoftWindows 11 23h2before 10.0.22631.707910.0.22631.7079
MicrosoftWindows 11 24h2before 10.0.26100.839010.0.26100.8390
MicrosoftWindows 11 25h2before 10.0.26200.839010.0.26200.8390
MicrosoftWindows 11 26h1before 10.0.28000.211310.0.28000.2113
MicrosoftWindows Server 2022 23h2before 10.0.25398.233010.0.25398.2330

Version data comes from the organisation that assigned the CVE. 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 CNA (microsoft.com).

Official description

Access of resource using incompatible type ('type confusion') in Windows Ancillary Function Driver for WinSock allows an authorized attacker to elevate privileges locally.

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

The underlying weakness: External Control of File Name or Path

The product allows user input to control or influence paths or file names that are used in filesystem operations.

How developers prevent this class of flaw

  • When the set of filenames is limited or known, create a mapping from a set of fixed input values (such as numeric IDs) to the actual filenames, and reject all other inputs. For example, ID 1 could map to inbox.txt and ID 2 could map to profile.txt. Features such as the ESAPI AccessReferenceMap provide this capability.
  • Run your code in a jail or similar sandbox environment that enforces strict boundaries between the process and the operating system. This may effectively restrict all access to files within a particular directory. Examples include the Unix chroot jail and AppArmor. In general, managed code may provide some protection. This may not be a feasible solution, and it only limits the impact to the operating system; the rest of your application may still be subject to compromise. Be careful to avoid CWE-243 and other weaknesses related to jails.
  • For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.

More External Control of File Name or Path vulnerabilities (CWE-73)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Recent External Control of File Name or Path vulnerabilities

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