CVE-2026-90391

Ioctl hang via false fault success

Published Sep 17, 2026 · Updated Sep 17, 2026

An infinite loop in Linux lib/test_hmm.c allows local users to hang a read or write ioctl after the mirrored address space exits. The dmirror_fault() function returns success when mmget_not_zero() fails, leaving the device page table entry absent and causing the caller to retry the same address indefinitely. Reachability requires access to the HMM test driver's device interface; the documented consequence is a non-progressing ioctl, not a demonstrated system crash.

CVSS severity4.8
Medium
EPSS probability0.21%
Next 30 days · Oct 19, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

An infinite loop in Linux lib/test_hmm.c allows local users to hang a read or write ioctl after the mirrored address space exits. The dmirror_fault() function returns success when mmget_not_zero() fails, leaving the device page table entry absent and causing the caller to retry the same address indefinitely. Reachability requires access to the HMM test driver's device interface; the documented consequence is a non-progressing ioctl, not a demonstrated system crash.

The record

CVE
CVE-2026-90391
Published
Sep 17, 2026
Updated
Sep 17, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 17, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 17, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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

  1. Affected versionversion=5.8
  2. Affected versionversion=b2ef9f5a5cb37643ca5def3516c546457074b882 <2636569ea7c19d9a40db4a1e8d0a027bdacf1569
  3. Affected versionversion=b2ef9f5a5cb37643ca5def3516c546457074b882 <50606ced303782f8715e2d0b98ca374ea498fa29
  4. Affected versionversion=b2ef9f5a5cb37643ca5def3516c546457074b882 <541a67f21ab807c8dbc0ea88d5a2eb73b2618090
  5. Affected versionversion=b2ef9f5a5cb37643ca5def3516c546457074b882 <6a8024511ddf4877435c34fb3d6028aa8e590649
  6. Affected versionversion=b2ef9f5a5cb37643ca5def3516c546457074b882 <701347e31aa607f3782403151a3125729d685275
  7. Affected versionversion=b2ef9f5a5cb37643ca5def3516c546457074b882 <a2074f86fc9653831e4fb7b711bb715db330f182
  8. Affected versionversion=b2ef9f5a5cb37643ca5def3516c546457074b882 <af7a6d6ec36a16a583ba2e4e9984c3cf1fe34655
  9. Affected versionversion=b2ef9f5a5cb37643ca5def3516c546457074b882 <d8e64ffab01e032ae29159d27230ace8cf8bdc80

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=5.8; version=b2ef9f5a5cb37643ca5def3516c546457074b882 <2636569ea7c19d9a40db4a1e8d0a027bdacf1569; version=b2ef9f5a5cb37643ca5def3516c546457074b882 <50606ced303782f8715e2d0b98ca374ea498fa29; version=b2ef9f5a5cb37643ca5def3516c546457074b882 <541a67f21ab807c8dbc0ea88d5a2eb73b2618090; version=b2ef9f5a5cb37643ca5def3516c546457074b882 <6a8024511ddf4877435c34fb3d6028aa8e590649; version=b2ef9f5a5cb37643ca5def3516c546457074b882 <701347e31aa607f3782403151a3125729d685275; version=b2ef9f5a5cb37643ca5def3516c546457074b882 <a2074f86fc9653831e4fb7b711bb715db330f182; version=b2ef9f5a5cb37643ca5def3516c546457074b882 <af7a6d6ec36a16a583ba2e4e9984c3cf1fe34655; version=b2ef9f5a5cb37643ca5def3516c546457074b882 <d8e64ffab01e032ae29159d27230ace8cf8bdc80

Published CVSS scores

3.3SUSECVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
4.8SUSECVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

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.

Activity data is delayed. The latest report is Sep 28, 2026.

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

No observations available

Sep 22, 2026Sep 28, 2026
Latest reporting daySep 28, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499Endpoint Denial of Service

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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