A vulnerability in the tdx-guest component causes the function enter_l2_vcpu to pass an incorrect RCX operand to the TDG.VP.ENTER TDCALL. This results in the TDX module receiving a VM index of 0 and misinterpreting invalidation control bits, potentially leading to escalation of privilege. The issue has a CVSS 4.0 base score of 4.6 (medium severity). It was fixed in version 0.3.1 by correcting the RCX value calculation.