ZDI-26-555: Parallels RAS Client RDP Backend Service Exposed Dangerous Function Local Privilege Escalation Vulnerability
ZDI discloses CVE-2026-18262, a CVSS 7.8 exposed dangerous function in Parallels RAS Client's RDP backend service allowing local privilege escalation.
ZDI advisory ZDI-26-555 describes an exposed dangerous function in the Parallels RAS Client RDP backend service, tracked as CVE-2026-18262 with a CVSS score of 7.8. The flaw allows local attackers to escalate privileges on affected installations. Exploitation requires first obtaining the ability to execute low-privileged code on the target system.
Remote Desktop Services Failures on Windows Servers Following September Update
September 2026 Patch Tuesday updates cause Windows Server 2019/2022/2025 RDS sessions to freeze, forcing administrators to roll back.
Cumulative updates KB5122876 (Windows Server 2019), KB5122882 (2022), and KB5122871 (2025) trigger Remote Desktop Services freezes hours after boot, with RDP connections hanging at 'Connecting…' and Event ID 20498 logged. Administrators trace the fault to an apparent deadlock in RDPSERVERBASE!WDLIB_Close during session teardown; only hard resets restore service and the issue recurs. The same September release patched roughly 973 vulnerabilities, including two actively exploited zero-days (CVE-2026-81963, CVE-2026-85880, both in CISA's KEV) and a critical RDS RCE, CVE-2026-69525 (CVSS 9.8). Workarounds include DISM-based removal of the update or an unofficial FeatureManagement registry key disabling the suspected audio-redirection code path; Microsoft has not yet confirmed the bug.