Xen Orchestra CVE-2026-110111

Requires (1) a valid authenticated Xen Orchestra account with any permission level, however low, and (2) the ability to make xo-server initiate an ESXi import (vm.importFromEsxi / vm.importMultipleFromEsxi) pointing at an attacker-controlled ESXi host serving a malicious .vmx file with a __proto__.permission property. The methods lack access-control checks, so no admin privileges are needed, but exploitation does require the attacker to host or control the ESXi endpoint that xo-server connects to and to drive the import workflow - this attacker-controlled-server requirement (reflected in AT:P/AC:H) is the primary limiting factor. Affected deployments are Xen Orchestra versions before 6.9.0; upgrading to 6.9.0 remediates.

This is a genuine high-priority privilege-escalation-to-RCE flaw, but with meaningful preconditions that temper raw urgency. The CVSS 4.0 vector (AV:N/AC:H/AT:P/PR:L/UI:N) and score of 7.7 (High) indicate network reachability but non-trivial exploitation: the attacker must already hold a valid low-privileged Xen Orchestra account (PR:L) and must satisfy an attack requirement (AT:P) - namely getting xo-server to connect to an attacker-controlled malicious ESXi host. The impact is severe (VC:H/VI:H/VA:H): global-administrator takeover plus remote code execution via Object.prototype pollution (CWE-1321). No EPSS score was provided, and there is no KEV listing and no indication of public exploit code, so there is no evidence of active exploitation - this is currently a patch-and-prioritize item rather than an emergency. The AC:H/AT:P requirements plus the need for prior authentication are the main factors keeping real-world risk below what the 'authenticated-to-admin RCE' headline suggests, though in multi-tenant or self-service XO deployments the PR:L barrier is low. Note: EPSS data is absent, so probabilistic exploitation likelihood could not be weighed; prioritize based on exposure of XO instances with multiple user accounts.

A low-privileged but authenticated Xen Orchestra user triggers the unprotected vm.importFromEsxi or vm.importMultipleFromEsxi method and directs xo-server to a malicious ESXi host under the attacker's control. That host serves a crafted .vmx file containing a __proto__.permission payload that pollutes Object.prototype, causing all permission-less accounts to inherit administrator rights and enabling remote code execution on xo-server. No public exploit code was identified at time of analysis, but the technique is well-documented conceptually in the advisory.