Security readout for executives and security teams
Plain-English summary
A Linux KVM flaw on LoongArch systems allows a negative virtual-CPU identifier to cause an out-of-bounds memory access. The supplied CVSS score is 8.8, indicating potentially serious confidentiality, integrity, and availability consequences. Exposure appears limited to LoongArch virtualization hosts using KVM, rather than Linux systems generally.
Executive priority
Treat as a high-priority infrastructure update where LoongArch KVM hosts run untrusted or lower-trust workloads. Patch promptly through supported distribution channels. Other Linux environments have no demonstrated exposure in the supplied evidence, so confirm architecture and KVM use before escalating broadly.
Technical view
kvm_get_vcpu_by_cpuid() accepts a signed integer but did not reject negative CPU identifiers before indexing kvm_arch::phyid_map::phys_map[]. Stable-kernel fixes return NULL for negative values, preventing the out-of-bounds access. The supplied vector describes local, low-privileged exploitation with low complexity, no user interaction, and scope change.
Likely exposure
Prioritize Linux hosts running KVM on LoongArch architecture. Systems on other architectures or not using LoongArch KVM are not shown as affected by this bundle. The supplied version data is ambiguous and includes unusual entries, so determine exposure using distribution advisories and inclusion of the referenced stable commits.
Exploitation context
The supplied record is not in CISA KEV, and the bundle provides no evidence of active exploitation or a public exploit. The CVSS vector indicates an attacker would need local, low-privileged access. The sources do not establish the precise attack path, reliability, or whether practical guest-to-host compromise has been demonstrated.
Researcher notes
The root issue is signed-input validation preceding an array lookup. The remediation adds a negative-cpuid rejection path. No CWE, crash trace, proof of concept, concrete exploitation primitive, or demonstrated security-boundary crossing is supplied. Version ranges appear insufficiently normalized; commit ancestry or vendor backport status is more reliable than raw version matching.
Mitigation direction
- Apply a vendor-supported kernel containing the relevant stable fix for your kernel branch.
- Check Linux distribution security guidance for corrected package versions and reboot requirements.
- Restrict untrusted access to affected LoongArch KVM virtualization hosts until patched.
- If patching is delayed, consider suspending exposed LoongArch KVM workloads after assessing operational impact.
Validation and detection
- Inventory LoongArch hosts and identify which systems have KVM enabled or loaded.
- Record running kernel versions and compare them with current distribution security advisories.
- Verify the installed kernel contains the applicable referenced stable commit or vendor backport.
- After updating, confirm hosts booted into the corrected kernel and KVM workloads operate normally.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
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CVE-2026-31558 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 8.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H26LinuxVulnerability scoring details
Base CVSS 3.1 score
8.8HighVector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
Source materials
- CVE List V5 sourceCVE List V5
- https://git.kernel.org/stable/c/596c3f8069c4792f22fce8c4452f44410032d910CVE reference, Linux
- https://git.kernel.org/stable/c/878cf6acb4fd8ab4126cf9d369a5bb0e23123418CVE reference, Linux
- https://git.kernel.org/stable/c/47857b05bd50db01e211a1b6f513d57901cd3e6bCVE reference, Linux
- https://git.kernel.org/stable/c/2db06c15d8c7a0ccb6108524e16cd9163753f354CVE reference, Linux
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.