CVE-2025-21632

Service interruption via unchecked shadow-stack register read

Published Jan 19, 2025 · Updated May 11, 2026

NULL pointer dereference in the Linux x86 FPU regset code allows local users to interrupt service through a shadow-stack ptrace request. The ssp_get() handler calls get_xsave_addr() without first applying ssp_active(), so disabled shadow stacks leave XFEATURE_CET_USER in its init state and produce a NULL address that triggers WARN_ON(). A local low-privileged user must trace a thread whose shadow stack is disabled; the published record reports a kernel warning and availability loss, not data disclosure or modification.

CVSS severity5.5
Medium
EPSS probability0.21%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

NULL pointer dereference in the Linux x86 FPU regset code allows local users to interrupt service through a shadow-stack ptrace request. The ssp_get() handler calls get_xsave_addr() without first applying ssp_active(), so disabled shadow stacks leave XFEATURE_CET_USER in its init state and produce a NULL address that triggers WARN_ON(). A local low-privileged user must trace a thread whose shadow stack is disabled; the published record reports a kernel warning and availability loss, not data disclosure or modification.

The record

CVE
CVE-2025-21632
Published
Jan 19, 2025
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-476, CWE-843, T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jan 19, 2025CVE publishedPublication date reported by the CVE source.
  2. May 11, 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=2fab02b25ae7cf5f714ab456b03d9a3fe5ae98c9 <0a3a872214188e4268d31581ed0cd44508e038cf
  2. Affected versionversion=2fab02b25ae7cf5f714ab456b03d9a3fe5ae98c9 <6bfe1fc22f462bec87422cdcbec4d7a2f43ff01d
  3. Affected versionversion=2fab02b25ae7cf5f714ab456b03d9a3fe5ae98c9 <a9d9c33132d49329ada647e4514d210d15e31d81
  4. Affected versionversion=6.6

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=2fab02b25ae7cf5f714ab456b03d9a3fe5ae98c9 <0a3a872214188e4268d31581ed0cd44508e038cf; version=2fab02b25ae7cf5f714ab456b03d9a3fe5ae98c9 <6bfe1fc22f462bec87422cdcbec4d7a2f43ff01d; version=2fab02b25ae7cf5f714ab456b03d9a3fe5ae98c9 <a9d9c33132d49329ada647e4514d210d15e31d81; version=6.6

Published CVSS scores

5.5NIST National Vulnerability DatabaseCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
4.4Amazon LinuxCVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-476NULL Pointer Dereference
CWE-843Access of Resource Using Incompatible Type ('Type Confusion')
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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