CVE-2026-33689

CriticalUpdated

Published: 17 April 2026

Published

17 April 2026

Modified

27 April 2026

KEV Added

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Patch

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CVSS Score 9.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H

EPSS Score 0.0018 39.4th percentile

Risk Priority 18 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2026-33689 is a critical-severity Out-of-bounds Read (CWE-125) vulnerability in Neutrinolabs Xrdp. Its CVSS base score is 9.1 (Critical).

Operationally, exploitation aligns with the MITRE ATT&CK technique Application or System Exploitation (T1499.004); ranked at the 39.4th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified are NIST 800-53 SI-10 (Information Input Validation) and SI-2 (Flaw Remediation).

Threat & Defense at a Glance

What attackers do: exploitation maps to Application or System Exploitation (T1499.004). What defenders deploy: see the NIST 800-53 controls recommended below.

Threat & Defense Details

Mitigating Controls (NIST 800-53 r5)AI

SI-10 Information Input Validation good match

prevent

Directly mitigates the out-of-bounds read by requiring validation of input buffer lengths in pre-authentication RDP message parsing before processing dynamic channel communications.

SI-2 Flaw Remediation good match

prevent

Ensures timely patching to xrdp version 0.10.6 or later, which fixes the insufficient input validation flaw.

SC-5 Denial-of-service Protection partial match

preventdetect

Limits the denial-of-service impact from process crashes caused by specially crafted RDP packets during initial connections.

MITRE ATT&CK Enterprise TechniquesAI

T1499.004 Application or System Exploitation Impact

Adversaries may exploit software vulnerabilities that can cause an application or system to crash and deny availability to users.

attack.mitre.org →

Why these techniques?

Remote unauthenticated exploitation causes process crash (DoS) via application vulnerability (T1499.004). Memory disclosure potential exists but too vague for specific technique mapping.

Confidence: HIGH · MITRE ATT&CK Enterprise v19.0

NVD Description

xrdp is an open source RDP server. Versions through 0.10.5 have an out-of-bounds read vulnerability in the pre-authentication RDP message parsing logic. A remote, unauthenticated attacker can trigger this flaw by sending a specially crafted sequence of packets during the…

initial connection phase. This vulnerability results from insufficient validation of input buffer lengths before processing dynamic channel communication. Successful exploitation can lead to a denial-of-service (DoS) condition via a process crash or potential disclosure of sensitive information from the service's memory space. This issue has been fixed in version 0.10.6.

Deeper analysisAI

CVE-2026-33689 is an out-of-bounds read vulnerability (CWE-125) in the pre-authentication RDP message parsing logic of xrdp, an open source RDP server. The flaw stems from insufficient validation of input buffer lengths before processing dynamic channel communication. It affects all versions of xrdp through 0.10.5.

A remote, unauthenticated attacker can exploit this vulnerability by sending a specially crafted sequence of packets during the initial connection phase. Successful exploitation may result in a denial-of-service condition through a process crash or potential disclosure of sensitive information from the service's memory space. The issue carries a CVSS v3.1 base score of 9.1 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H), highlighting its high severity due to network accessibility, low attack complexity, and impacts on both confidentiality and availability.

The vulnerability has been addressed in xrdp version 0.10.6, as detailed in the project's release notes and security advisory. Security practitioners should update to this version or later to mitigate the risk.