CVE-2026-55639 neutrinolabs CVE debrief

Who should care

Users of xrdp versions 0.10.6 and prior should apply the patch or upgrade to version 0.10.6.1 or later. Additionally, system administrators and security teams responsible for managing and securing RDP services should be aware of this vulnerability and take necessary precautions.

Technical summary

The xrdp process fails to perform sufficient length validation for the incoming data block during the initial capability and security negotiation phase. A remote, unauthenticated attacker could potentially exploit this flaw by sending a specially crafted RDP packet containing malformed data. Due to missing bounds checks, the xrdp process may read a small number of bytes beyond the declared data block boundary, potentially disclosing process memory contents. This issue has been fixed in version 0.10.6.1, and users of xrdp versions 0.10.6 and prior should apply the patch or upgrade to prevent potential memory disclosure.

Defensive priority

Medium-priority defensive actions are recommended due to the potential for memory disclosure.

Recommended defensive actions

• Apply the patch or upgrade to version 0.10.6.1 or later
• Restrict access to the xrdp service
• Monitor for suspicious RDP activity
• Implement additional security measures such as network segmentation and intrusion detection
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented

Evidence notes

The CVE-2026-55639 issue concerns a vulnerability in xrdp, an open-source RDP server, specifically in the parsing of Client Security Data within the Client MCS Connect Initial PDU with GCC Conference Create Request. The parser fails to perform sufficient length validation for the incoming data block, potentially allowing a remote, unauthenticated attacker to disclose process memory contents by sending a specially crafted RDP packet. This issue has been fixed in version 0.10.6.1.

Official resources