Low severity2.9NVD Advisory· Published Jan 28, 2026· Updated Jun 17, 2026
CVE-2026-23553
CVE-2026-23553
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.
AI Insight
LLM-synthesized narrative grounded in this CVE's description and references.
Affected products
12- osv-coords9 versionspkg:rpm/opensuse/xen&distro=openSUSE%20Leap%2015.6pkg:rpm/opensuse/xen&distro=openSUSE%20Tumbleweedpkg:rpm/suse/xen&distro=SUSE%20Linux%20Enterprise%20Micro%205.2pkg:rpm/suse/xen&distro=SUSE%20Linux%20Enterprise%20Micro%205.3pkg:rpm/suse/xen&distro=SUSE%20Linux%20Enterprise%20Micro%205.4pkg:rpm/suse/xen&distro=SUSE%20Linux%20Enterprise%20Micro%205.5pkg:rpm/suse/xen&distro=SUSE%20Linux%20Enterprise%20Module%20for%20Basesystem%2015%20SP7pkg:rpm/suse/xen&distro=SUSE%20Linux%20Enterprise%20Module%20for%20Server%20Applications%2015%20SP7pkg:rpm/suse/xen&distro=SUSE%20Linux%20Enterprise%20Server%20LTSS%20Extended%20Security%2012%20SP5
< 4.18.5_10-150600.3.37.1+ 8 more
- (no CPE)range: < 4.18.5_10-150600.3.37.1
- (no CPE)range: < 4.21.0_04-1.1
- (no CPE)range: < 4.14.6_28-150300.3.94.1
- (no CPE)range: < 4.16.7_06-150400.4.78.1
- (no CPE)range: < 4.16.7_06-150400.4.78.1
- (no CPE)range: < 4.17.6_04-150500.3.59.1
- (no CPE)range: < 4.20.2_04-150700.3.22.1
- (no CPE)range: < 4.20.2_04-150700.3.22.1
- (no CPE)range: < 4.12.4_64-3.137.1
Patches
Vulnerability mechanics
References
3- www.openwall.com/lists/oss-security/2026/01/27/3nvdMailing ListMitigationPatchThird Party Advisory
- xenbits.xen.org/xsa/advisory-479.htmlnvdMitigationPatchVendor Advisory
- xenbits.xenproject.org/xsa/advisory-479.htmlnvdMitigationPatchVendor Advisory
News mentions
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