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.
CVSS Details
- CVSS 3.1 Base Score: 4.7
- CVSS 3.1 Vector: (CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N)
Covered by Rapid7
| Product | Vendor Advisory | Solution File | Added | Published |
|---|---|---|---|---|
| Alpine Linux | — | Upgrade xen | Mar 26, 2024 | Jan 5, 2024 |
| Debian | — | Upgrade xen | Jul 30, 2024 | Jan 5, 2024 |
| Dell Powerstore Dsa2024158 | — | Upgrade Dell PowerStoreOS to the latest version | Jan 13, 2026 | Apr 4, 2024 |
| Dell Powerstore Dsa2024225 | — | Upgrade Dell PowerStoreOS to the latest version | Oct 23, 2025 | May 29, 2024 |
| Gentoo Linux | — | Upgrade app-emulation/xen. | Sep 23, 2024 | Jan 5, 2024 |
| Suse | — | Upgrade xen-doc-htmlUpgrade xen-libs-32bitUpgrade xen-tools-xendomains-wait-diskUpgrade xenUpgrade xen-toolsUpgrade xen-libsUpgrade xen-develUpgrade xen-tools-domu | Nov 17, 2023 | Nov 16, 2023 |
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