xen: The fixes for XSA-422 (Branch Type Confusion) and XSA-434 (Speculative Return Stack Overflow) are not IRQ-safe
CVE-2023-46836 is fixed in xen on 1 platform, first by DEBIAN-CVE-2023-46836, released January 5, 2024. It is not reported as exploited. Patch Radar priority: Routine.
The fixes for XSA-422 (Branch Type Confusion) and XSA-434 (Speculative Return Stack Overflow) are not IRQ-safe. It was believed that the mitigations always operated in contexts with IRQs disabled. However, the original XSA-254 fix for Meltdown (XPTI) deliberately left interrupts enabled on two entry paths; one unconditionally, and one conditionally on whether XPTI was active. As BTC/SRSO and Meltdown affect different CPU vendors, the mitigations are not active together by default. Therefore, there is a race condition whereby a malicious PV guest can bypass BTC/SRSO protections and launch a BTC/SRSO attack against Xen.
Where it's fixed
| Product | Fixed in | Fix | Released |
|---|---|---|---|
| Linux | |||
| xen · Debian 12.15 (bookworm) | 4.17.2+76-ge1f9cb16e2-1~deb12u1 | DEBIAN-CVE-2023-46836 | Jan 5, 2024 |
| xen · Debian 13.5 (trixie) | 4.17.2+76-ge1f9cb16e2-1 | DEBIAN-CVE-2023-46836 | Jan 5, 2024 |
| xen · Debian 14 | 4.17.2+76-ge1f9cb16e2-1 | DEBIAN-CVE-2023-46836 | Jan 5, 2024 |
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