vulnerability
Alpine Linux: CVE-2026-23553: Improper Initialization
| Severity | CVSS | Published | Added | Modified |
|---|---|---|---|---|
| 2 | (AV:L/AC:M/Au:N/C:P/I:N/A:N) | Jan 28, 2026 | Jan 29, 2026 | Feb 10, 2026 |
Severity
2
CVSS
(AV:L/AC:M/Au:N/C:P/I:N/A:N)
Published
Jan 28, 2026
Added
Jan 29, 2026
Modified
Feb 10, 2026
Description
In the context switch logic Xen attempts to skip an IBPB in the case of
a vCPU returning to a CPU on which it was the previous vCPU to run.
While safe for Xen's isolation between vCPUs, this prevents the guest
kernel correctly isolating between tasks. Consider:
1) vCPU runs on CPU A, running task 1.
2) vCPU moves to CPU B, idle gets scheduled on A. Xen skips IBPB.
3) On CPU B, guest kernel switches from task 1 to 2, issuing IBPB.
4) vCPU moves back to CPU A. Xen skips IBPB again.
Now, task 2 is running on CPU A with task 1's training still in the BTB.
a vCPU returning to a CPU on which it was the previous vCPU to run.
While safe for Xen's isolation between vCPUs, this prevents the guest
kernel correctly isolating between tasks. Consider:
1) vCPU runs on CPU A, running task 1.
2) vCPU moves to CPU B, idle gets scheduled on A. Xen skips IBPB.
3) On CPU B, guest kernel switches from task 1 to 2, issuing IBPB.
4) vCPU moves back to CPU A. Xen skips IBPB again.
Now, task 2 is running on CPU A with task 1's training still in the BTB.
Solution
alpine-linux-upgrade-xen
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