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High

Remote Code Execution in Windows Remote Desktop Client

IdentifiersCVE-2025-29966CWE-122· Heap-based Buffer Overflow

CVE-2025-29966 is a critical heap-based buffer overflow in the Windows Remote Desktop Client. The provided content describes the flaw as occurring in the mstscax.dll component during the RDP session initialization sequence, where improper memory handling and insufficient validation of dynamically allocated buffer sizes allow a malicious RDP server to send oversized RDP packets that corrupt heap memory. The resulting memory corruption can overwrite adjacent structures and critical pointers, leading to arbitrary code execution on the client system. Multiple sources in the content characterize this as a Remote Desktop Client RCE vulnerability with CVSS 8.8 and note that exploitation is triggered when a vulnerable client connects to an attacker-controlled or malicious RDP server.

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ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

Successful exploitation allows remote arbitrary code execution on the vulnerable Windows system running the Remote Desktop Client. The content further states that exploitation can yield SYSTEM-level privileges, giving an attacker full control of the affected host. In practical terms, this can enable malware deployment, persistence, credential theft, lateral movement, and full compromise of enterprise endpoints that initiate RDP connections to attacker-controlled servers.

Mitigation

If you can’t patch tonight, do this now.

If immediate patching is not possible, restrict RDP connectivity to trusted IP addresses and trusted servers only. Enable Network Level Authentication where applicable, although the content does not establish that NLA fully prevents exploitation of this client-side flaw. Use IPS/virtual patching controls to detect or block malicious RDP traffic. Monitor for anomalous RDP activity, including unusual or oversized initialization packets, rapid connection attempts, unexpected SYSTEM-level process creation, and suspicious privilege-escalation behavior on client hosts.

Remediation

Patch, then assume compromise.

Apply Microsoft’s security update for CVE-2025-29966. The provided content states Microsoft released update KB5002695 as part of the May 2025 Patch Tuesday and recommends deploying it through Windows Update or enterprise patch management tooling as soon as possible. Prioritize systems that use the Remote Desktop Client to connect to untrusted, external, or third-party RDP endpoints.
PUBLIC EXPLOITS

Exploits

No public exploits tracked yet. Mallory keeps watching.

VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

EXPOSURE SURFACE

Affected products & vendors

Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.

VendorProductType
Microsoft CorporationRemote Desktopapplication
Microsoft CorporationWindows 10 1507operating_system
Microsoft CorporationWindows 10 1607operating_system
Microsoft CorporationWindows 10 1809operating_system
Microsoft CorporationWindows 10 21h2operating_system
Microsoft CorporationWindows 10 22h2operating_system
Microsoft CorporationWindows 11 22h2operating_system
Microsoft CorporationWindows 11 23h2operating_system
Microsoft CorporationWindows 11 24h2operating_system
Microsoft CorporationWindows Appapplication
Microsoft CorporationWindows App Client For Windows Desktopapplication
Microsoft CorporationWindows Server 2008operating_system
Microsoft CorporationWindows Server 2008 R2operating_system
Microsoft CorporationWindows Server 2012operating_system
Microsoft CorporationWindows Server 2012 R2operating_system
Microsoft CorporationWindows Server 2016operating_system
Microsoft CorporationWindows Server 2019operating_system
Microsoft CorporationWindows Server 2022operating_system
Microsoft CorporationWindows Server 2022 23h2operating_system
Microsoft CorporationWindows Server 2025operating_system
Microsoft CorporationWindows Server 23h2operating_system

Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.

ACTIVITY FEED

Recent activity

9 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.

9 SOURCESView more in app
+3 more in the timeline
What this page doesn’t show

The version that knows your environment.

This page is what’s public. Mallory adds the parts that aren’t: which of your assets are affected, which adversaries are exploiting it right now, which detections to deploy, and what to do tonight.
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Exposure mapping

Query your assets running an affected version, and investigate the blast radius.

Threat actor evidence

Every observed campaign linking this CVE to a named adversary.

Associated malware

Malware families riding this exploit, with evidence and IOCs.

Detection signatures

YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.

Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

Social activity2

Community discussion across Reddit, Mastodon, and other social sources.

EXTERNAL REFERENCES
MITRE CVE
cve.org · CVE-2025-29966
NVD
nvd.nist.gov/vuln/detail/CVE-2025-29966
MITRE CWE · CWE-122
Heap-based Buffer Overflow
Vendor Advisory
msrc.microsoft.com/update-guide/vulnerability/CVE-2025-29966