Security Resilience

CVE-2026-23558

Race Condition in Xen ≥ 4.0.0

Published
19 May 2026
Modified
14 October 2026
Patch / advisory
CVSS Score v3.1 7.8
Click a component to see what it means
Raw vectorCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H
EPSS Score 0.0012 2th percentile
Risk Priority 52 floored blend · peak EPSS

CVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.

Summary

CVE-2026-23558 is a high-severity Race Condition (CWE-362) vulnerability in Xen Xen. Its CVSS base score is 7.8 (High).

Operationally, ranked at the 2th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified map to SC-39 (Process Isolation) and SC-4 (Information in Shared System Resources) — see the control section below for these in your framework.

OWASP Top 10 for Web (2025)

EU & UK References

Vulnerability Data

The adjustments made for XSA-379 as well as those subsequently becoming XSA-387 still left a race window, when a HVM or PVH guest does a grant table version change from v2 to v1 in parallel with mapping the status page(s)…

more

via XENMEM_add_to_physmap. Some of the status pages may then be freed while mappings of them would still be inserted into the guest's secondary (P2M) page tables.

CWE(s)

Related Threats

CVEs Like This One

CVE-2025-58145Same product: Xen Xen
CVE-2025-58149Same product: Xen Xen
CVE-2023-34325Same product: Xen Xen
CVE-2024-31143Same product: Xen Xen
CVE-2026-23557Same product: Xen Xen
CVE-2023-34328Same product: Xen Xen
CVE-2023-34326Same product: Xen Xen
CVE-2025-58150Same product: Xen Xen
CVE-2023-46837Same product: Xen Xen
CVE-2025-27465Same product: Xen Xen

Affected Assets

xen
xen
≥ 4.0.0

Mitigating Controls

Mitigating Controls (NIST 800-53 r5) AI

Maintaining separate execution domains for each process structurally eliminates unintended concurrent access to the same shared resources.

Preventing unintended information transfer through shared system resources directly addresses the improper concurrent modification that defines a race condition.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

blocks

A.8.25 mandates secure SDLC practices (secure coding guidelines, security requirements, checkpoints, testing including code scans/penetration tests, developer training) that reach race conditions in concurrent code, but only as one slice of a broad requirement whose implementation scope and rigour are left to the organisation.

blocks

A.8.26 explicitly lists resilience against malicious attacks including SQL injections and input validation as application security requirements to identify/address; race conditions are a similar class of timing-based concurrency flaw that can be mitigated by requirements for proper synchronization/locking, but this is only one slice of the broad CWE-362 class (most instances arise in low-level shared-memory or TOCTOU scenarios not named here).

blocks

Secure architecture principles require proper synchronization and resource isolation, addressing the root cause of CWE-362.

prevents

Secure coding standards explicitly forbid unsafe concurrent access patterns and mandate atomic operations or locks.

finds

Security testing can detect race conditions, but does not prevent them at design or coding time.

Hardening callouts derived

DISA STIG baselines are authored against specific weaknesses. Where this CVE cites a broad weakness class, the mapping is not asserted at that abstraction (owner ruling, 2026-09-25: grade only at Base and below), so no rule is shown here rather than a rule shown against the wrong grain.

  • No fine-grained STIG row for CWE-362, a class-level weakness, and none of its children carries one either.

References