CyberSecBulletin
CVE-2026-42909NVD status: Modified

Remote Desktop client for Windows Desktop: Out-of-bounds Write

Published Updated By the CyberSecBulletin desk

CVE-2026-42909 is a high-severity out-of-bounds write vulnerability in Remote Desktop client for Windows Desktop from Microsoft, with a CVSS 3.1 base score of 7.5 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, but only if a user takes part, for example by opening a link or file. The record lists version 1.2.7214.0 as the first without the flaw, so updating Remote Desktop client for Windows Desktop to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.4% 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 Remote Desktop client for Windows Desktop to 1.2.7214.0 or a later version.
  2. Update Windows 10 Version 1607 to 10.0.14393.9234 or a later version.
  3. Update Windows 10 Version 1809 to 10.0.17763.8880 or a later version.
  4. Read the advisory on msrc.microsoft.com for workarounds and exact fixed builds.
  5. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
  6. Because the attack needs a user to take part, warn users about unexpected links and files related to this product until it is patched.

Affected products and versions

VendorProductAffected versionsFixed in
MicrosoftRemote Desktop client for Windows Desktop1.2.0.0 up to, but not including, 1.2.7214.01.2.7214.0
MicrosoftWindows 10 Version 160710.0.14393.0 up to, but not including, 10.0.14393.923410.0.14393.9234
MicrosoftWindows 10 Version 180910.0.17763.0 up to, but not including, 10.0.17763.888010.0.17763.8880
MicrosoftWindows 10 Version 21H210.0.19044.0 up to, but not including, 10.0.19044.741710.0.19044.7417
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, 10.0.22631.721910.0.22631.7219
MicrosoftWindows 11 Version 24H210.0.26100.0 up to, but not including, 10.0.26100.865510.0.26100.8655
MicrosoftWindows 11 Version 25H210.0.26200.0 up to, but not including, 10.0.26200.865510.0.26200.8655
MicrosoftWindows 11 version 26H110.0.28000.0 up to, but not including, 10.0.28000.226910.0.28000.2269
MicrosoftWindows App Client for Windows Desktop1.00 up to, but not including, 2.0.1193.02.0.1193.0
MicrosoftWindows Server 20126.2.9200.0 up to, but not including, 6.2.9200.261326.2.9200.26132
MicrosoftWindows Server 2012 (Server Core installation)6.2.9200.0 up to, but not including, 6.2.9200.261326.2.9200.26132
MicrosoftWindows Server 2012 R26.3.9600.0 up to, but not including, 6.3.9600.232286.3.9600.23228
MicrosoftWindows Server 2012 R2 (Server Core installation)6.3.9600.0 up to, but not including, 6.3.9600.232286.3.9600.23228
MicrosoftWindows Server 201610.0.14393.0 up to, but not including, 10.0.14393.923410.0.14393.9234
MicrosoftWindows Server 2016 (Server Core installation)10.0.14393.0 up to, but not including, 10.0.14393.923410.0.14393.9234
MicrosoftWindows Server 201910.0.17763.0 up to, but not including, 10.0.17763.888010.0.17763.8880
MicrosoftWindows Server 2019 (Server Core installation)10.0.17763.0 up to, but not including, 10.0.17763.888010.0.17763.8880
MicrosoftWindows Server 202210.0.20348.0 up to, but not including, 10.0.20348.525610.0.20348.5256
MicrosoftWindows Server 202510.0.26100.0 up to, but not including, 10.0.26100.3299510.0.26100.32995
MicrosoftWindows Server 2025 (Server Core installation)10.0.26100.0 up to, but not including, 10.0.26100.3299510.0.26100.32995
MicrosoftRemote Desktop Clientbefore 1.2.72141.2.7214
MicrosoftWindows Appbefore 2.0.1193.02.0.1193.0
MicrosoftWindows 10 1607before 10.0.14393.923410.0.14393.9234
MicrosoftWindows 10 1809before 10.0.17763.888010.0.17763.8880

Version data comes from the organisation that assigned the CVE; 6 further products are omitted here. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
HighSuccess depends on conditions outside the attacker's control.
Privileges required
NoneNo account or login is needed.
User interaction
RequiredA user must take an action such as opening a file or link.
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:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H. Scored by CNA (microsoft.com).

Official description

Concurrent execution using shared resource with improper synchronization ('race condition') in Remote Desktop Client allows an unauthorized attacker to execute code over a network.

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

The underlying weakness: Out-of-bounds Write

The product writes data past the end, or before the beginning, of the intended buffer.

How developers prevent this class of flaw

  • Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow protection, but the protection can be disabled by the programmer. Be wary that a language's interface to native code may still be subject to overflows, even if the language itself is theoretically safe.
  • Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. Examples include the Safe C String Library (SafeStr) by Messier and Viega, and the Strsafe.h library from Microsoft. These libraries provide safer versions of overflow-prone string-handling functions.
  • Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking. D3-SFCV (Stack Frame Canary Validation) from D3FEND discusses canary-based detection in detail.

More Out-of-bounds Write vulnerabilities (CWE-787)

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

Other vulnerabilities in Remote Desktop client for Windows Desktop

All Remote Desktop client for Windows Desktop vulnerabilities

Recent Out-of-bounds Write vulnerabilities

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