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PatchSiren cyber security CVE debrief

CVE-2026-42909 Microsoft CVE debrief

CVE-2026-42909 is a high-severity vulnerability in the Remote Desktop Client that allows an unauthorized attacker to execute code over a network. The vulnerability is caused by a heap-based buffer overflow and has a CVSS score of 7.5.

Vendor
Microsoft
Product
Remote Desktop client for Windows Desktop
CVSS
HIGH 7.5
CISA KEV
Not listed in stored evidence
Original CVE published
2026-06-09
Original CVE updated
2026-07-09
Advisory published
2026-06-09
Advisory updated
2026-07-09

Who should care

Administrators and users of Microsoft Remote Desktop Client and affected Windows versions should be aware of this vulnerability and take necessary actions to mitigate it.

Technical summary

The vulnerability is a heap-based buffer overflow in the Remote Desktop Client, which allows an unauthorized attacker to execute code over a network. The CVSS vector is CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H.

Defensive priority

High

Recommended defensive actions

  • Apply patches and updates from Microsoft as soon as possible.
  • Use secure communication protocols and authenticate users before allowing access to the Remote Desktop Client.
  • Monitor and limit access to sensitive data and systems.

Evidence notes

The vulnerability affects multiple versions of Windows and Remote Desktop Client. See the CPE criteria in the source item for more information.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-42909 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-42909

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-42909 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-42909

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.