CVE-2026-50497: Windows RDP Information Disclosure Flaw

CVE-2026-50497 Overview

CVE-2026-50497 is an information disclosure vulnerability in the Windows Remote Desktop Protocol (RDP) caused by an off-by-one error [CWE-193]. An unauthorized attacker can exploit this flaw over a network to disclose sensitive information from the RDP service. Successful exploitation requires user interaction, which limits opportunistic attacks but remains viable in phishing and social engineering scenarios.

Microsoft published the advisory on July 14, 2026, and updated it on July 16, 2026. The vulnerability affects the confidentiality of the target system without impacting integrity or availability. No public proof-of-concept exploit is currently available, and the flaw is not listed in the CISA Known Exploited Vulnerabilities catalog.

Critical Impact
A network-based attacker can leak confidential memory contents from the Windows RDP service by triggering an off-by-one read condition, potentially exposing credentials, session data, or protocol state information.

Affected Products

Microsoft Windows (Remote Desktop Protocol component)
Specific Windows versions to be confirmed via the Microsoft Security Response Center advisory
Systems exposing RDP services to untrusted networks

Discovery Timeline

2026-07-14 - CVE-2026-50497 published to NVD
2026-07-16 - Last updated in NVD database

Technical Details for CVE-2026-50497

Vulnerability Analysis

The vulnerability is an off-by-one error [CWE-193] within the Windows Remote Desktop Protocol implementation. Off-by-one errors occur when a loop, index calculation, or buffer boundary check is miscomputed by a single element or byte. In RDP, this results in reading data beyond the intended boundary of an internal buffer.

The attack occurs over the network and requires user interaction to succeed. The scope remains unchanged, meaning the exploited component and the impacted component are the same. Only confidentiality is affected, so the attacker gains the ability to read memory contents but cannot modify system state or crash the service through this flaw.

Disclosed memory may contain fragments of protocol structures, session identifiers, or adjacent heap data. Attackers can repeatedly trigger the condition to accumulate leaked bytes over time.

Root Cause

The root cause is an incorrect boundary calculation in code that processes RDP protocol data. The condition likely appears in a length check or loop terminator where the comparison uses the wrong operator or index. This allows an additional byte or element to be read from adjacent memory during protocol handling.

Attack Vector

An attacker must convince a user to initiate an RDP connection to a malicious server, or otherwise interact with an attacker-controlled RDP endpoint. Once the connection is established, the attacker manipulates protocol messages to trigger the off-by-one read. The leaked bytes are returned to the attacker through subsequent protocol responses or error conditions.

Refer to the Microsoft Security Update for authoritative technical details as they become available.

Detection Methods for CVE-2026-50497

Indicators of Compromise

Outbound RDP (TCP/UDP port 3389) connections from workstations to untrusted or unexpected external hosts
RDP client processes (mstsc.exe) launched from unusual parent processes such as email clients or browsers
Malformed or truncated RDP protocol negotiation messages recorded in network captures

Detection Strategies

Inspect RDP traffic for anomalous handshake sequences and protocol structures that deviate from RFC-compliant behavior
Correlate user-initiated RDP sessions with recent phishing indicators such as suspicious email attachments or link clicks
Monitor for RDP client executions triggered by .rdp file attachments delivered through email or downloaded from the web

Monitoring Recommendations

Enable Windows event logging for Remote Desktop Client events (Event ID 1024, 1026) and forward to a centralized SIEM
Capture NetFlow or packet metadata on egress firewalls for all outbound RDP traffic and alert on connections to non-corporate destinations
Deploy network intrusion detection signatures targeting anomalous RDP protocol negotiation once vendor signatures become available

How to Mitigate CVE-2026-50497

Immediate Actions Required

Apply the Microsoft security update referenced in the Microsoft Security Update advisory as soon as it is available in your maintenance window
Block outbound RDP connections (TCP/UDP 3389) at perimeter firewalls except to explicitly approved destinations
Educate users to avoid opening .rdp files from untrusted sources and to verify remote desktop destinations before connecting

Patch Information

Microsoft addresses this vulnerability through its standard security update channels. Administrators should consult the Microsoft Security Update advisory for the list of affected products, patched build numbers, and superseded updates. Apply updates via Windows Update, Windows Server Update Services (WSUS), or your preferred patch management platform.

Workarounds

Restrict RDP client usage to authorized administrators through Group Policy or AppLocker rules targeting mstsc.exe
Configure email security gateways to strip or quarantine .rdp file attachments
Use Remote Desktop Gateway with strict destination allow-lists to prevent connections to arbitrary external RDP servers

bash

# Example: Block outbound RDP to non-corporate networks using Windows Firewall
New-NetFirewallRule -DisplayName "Block Outbound RDP to Untrusted" `
  -Direction Outbound `
  -Protocol TCP `
  -RemotePort 3389 `
  -RemoteAddress Internet `
  -Action Block `
  -Profile Any