What’s Vulnerable › Vulnerabilities

CVE-2023-46836: x86: BTC/SRSO fixes not fully effective

• Severity: medium (CVSS 4.7 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2024-01-05 · updated 2026-06-17

Description

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.

Affected products

• xen: all versions

References

• https://xenbits.xenproject.org/xsa/advisory-446.html
• http://xenbits.xen.org/xsa/advisory-446.html
• https://xenbits.xenproject.org/xsa/advisory-446.html

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