CVE-2023-46836

Name	CVE-2023-46836
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.
Source	CVE (at NVD; CERT, LWN, oss-sec, fulldisc, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)
Debian Bugs	1056928

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
xen (PTS)	bullseye	4.14.6-1	vulnerable
	bullseye (security)	4.14.5+94-ge49571868d-1	vulnerable
	bookworm	4.17.3+10-g091466ba55-1~deb12u1	fixed
	bookworm (security)	4.17.5+23-ga4e5191dc0-1	fixed
	sid, trixie	4.19.1-1	fixed

The information below is based on the following data on fixed versions.

Package	Type	Release	Fixed Version	Urgency	Debian Bugs
xen	source	buster	(unfixed)	end-of-life
xen	source	bullseye	(unfixed)	end-of-life
xen	source	bookworm	4.17.2+76-ge1f9cb16e2-1~deb12u1
xen	source	(unstable)	4.17.2+76-ge1f9cb16e2-1		1056928

[bullseye] - xen <end-of-life> (EOLed in Bullseye)
[buster] - xen <end-of-life> (DSA 4677-1)
https://xenbits.xen.org/xsa/advisory-446.html