CVE-2026-31788

Kernel-lockdown bypass via unrestricted privcmd hypercalls

Published Mar 25, 2026 · Updated Mar 25, 2026

Kernel-lockdown bypass in the Xen privcmd driver in Linux Kernel allows local users to modify protected kernel memory. The driver accepts arbitrary user-space hypercalls without initially constraining a non-dom0 guest to its Xenstore target domain. Reachability requires administrator privileges inside a secure-booted Xen PV, PVH, or HVM Linux guest; the bypass undermines that guest rather than the host.

CVSS severity8.2
High
EPSS probability0.15%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Kernel-lockdown bypass in the Xen privcmd driver in Linux Kernel allows local users to modify protected kernel memory. The driver accepts arbitrary user-space hypercalls without initially constraining a non-dom0 guest to its Xenstore target domain. Reachability requires administrator privileges inside a secure-booted Xen PV, PVH, or HVM Linux guest; the bypass undermines that guest rather than the host.

The record

CVE
CVE-2026-31788
Published
Mar 25, 2026
Updated
Mar 25, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
T1562.001
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. Mar 25, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 25, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <1879319d790f7d57622cdc22807b60ea78b56b6d
  2. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <389bae9a4409934e8b8d4dbdaaf02a3ae71cf8e4
  3. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <78432d8f0372c71c518096395537fa12be7ff24e
  4. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <87a803edb2ded911cb587c53bff179d2a2ed2a28
  5. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <cbede2e833da1893afbea9b3ff29b5dda23a4a91

What conditions does exploitation require?

Attack vectorlocal
Required privilegesadmin

What is affected?

The Linux Kernel Organization · Linux Kernelversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <1879319d790f7d57622cdc22807b60ea78b56b6d; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <389bae9a4409934e8b8d4dbdaaf02a3ae71cf8e4; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <78432d8f0372c71c518096395537fa12be7ff24e; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <87a803edb2ded911cb587c53bff179d2a2ed2a28; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <cbede2e833da1893afbea9b3ff29b5dda23a4a91

Published CVSS scores

8.2kernel.orgCVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1562.001Impair Defenses: Disable or Modify Tools

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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