Raw vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:HCVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.
Summary
CVE-2026-31568 is a high-severity Out-of-bounds Read (CWE-125) vulnerability in Linux Linux Kernel. Its CVSS base score is 7.1 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked at the 5th 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 SA-11 (Developer Testing and Evaluation) and SA-8 (Security and Privacy Engineering Principles) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-31568 is a vulnerability in the Linux kernel's s390/mm component, affecting IBM Z/s390 architecture systems. It stems from missing fixups for secure storage access exceptions on pages donated to the Ultravisor that lack the PG_arch_1 bit, which indicates non-exported guest secure storage. Without the bit set, prior kernel behavior incorrectly assumes the page is already exported via arch_make_folio_accessible(), leading to unresolvable secure storage access exception loops.
A local attacker with low privileges (PR:L) can exploit this vulnerability with low complexity (AC:L) and no user interaction (UI:N), requiring only local access (AV:L) on an unchanged scope (S:U) system. Successful exploitation yields high confidentiality impact (C:H), potentially exposing sensitive secure storage data, and high availability impact (A:H) through denial-of-service via infinite exception loops. The issue aligns with CWE-125 (Out-of-bounds Read).
Mitigation requires applying the relevant Linux kernel stable patches, as detailed in the commit references: https://git.kernel.org/stable/c/43ac2d18db1131df0a89993f709131ebfc29f3bd, https://git.kernel.org/stable/c/b00be77302d7ec4ad0367bb236494fce7172b730, and https://git.kernel.org/stable/c/b36b0e804aee5f20c6798dbeaeaa7cfdb7c6cf88. These patches unconditionally attempt to export the page and provide fixups if export fails, resolving the exception loops. The vulnerability was published on 2026-04-24 with a CVSS v3.1 base score of 7.1.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-25461
Vulnerability Data
In the Linux kernel, the following vulnerability has been resolved: s390/mm: Add missing secure storage access fixups for donated memory There are special cases where secure storage access exceptions happen in a kernel context for pages that don't have the…
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PG_arch_1 bit set. That bit is set for non-exported guest secure storage (memory) but is absent on storage donated to the Ultravisor since the kernel isn't allowed to export donated pages. Prior to this patch we would try to export the page by calling arch_make_folio_accessible() which would instantly return since the arch bit is absent signifying that the page was already exported and no further action is necessary. This leads to secure storage access exception loops which can never be resolved. With this patch we unconditionally try to export and if that fails we fixup.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Developer testing and evaluation directly finds out-of-bounds read flaws through static analysis, fuzzing, and dynamic bounds checks.
Secure engineering principles require bounds checking and memory-safe constructs that stop out-of-bounds reads from being introduced.
Process isolation confines the effects of an out-of-bounds read to the compromised process.
Input validation rejects malformed indices or lengths that would otherwise cause reads outside buffer bounds.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Secure-development practices such as bounds checking and memory-safe languages directly prevent out-of-bounds reads.
Vulnerability scanning and recording can discover instances of out-of-bounds reads after code is deployed.
Routine patching replaces vulnerable code containing out-of-bounds read flaws.
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.
Security testing in development and acceptance includes fuzzing and static analysis that detect out-of-bounds read defects before release.
Logging can record evidence of an out-of-bounds read but does not prevent the weakness itself.
Secure coding standards explicitly forbid unsafe pointer arithmetic and mandate bounds-checked reads, eliminating CWE-125.