CVE-2023-46836

Summary

CVE-2023-46836 reveals a race condition vulnerability in Xen's mitigations for the XSA-422 (Branch Type Confusion) and XSA-434 (Speculative Return Stack Overflow) vulnerabilities. Previously believed to operate only when IRQs were disabled, these mitigations were found to have IRQ-unsafe fixes, allowing a malicious PV guest to bypass BTC/SRSO protections and launch attacks against Xen. The issue stems from the XPTI fix for Meltdown, which unintentionally left interrupts enabled on certain entry paths. Despite affecting different CPU vendors, the mitigations are not active together by default, increasing the risk of exploitation.

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