CVE-2026-89593

Reservation-count underflow during shared-folio unmapping

Published Sep 11, 2026 · Updated Sep 11, 2026

Reservation-accounting error in Linux 6.9 allows local users to underflow the hugetlb reserved-page count during shared-folio unmapping. __unmap_hugepage_range() adjusts the reservation while a huge-page folio remains mapped by another process because it does not first require a zero mapcount. Triggering requires the folio to be mapped in both a parent and child, with the parent unmapping first; no crash or privilege gain is reported.

CVSS severityUnavailable
Unscored
EPSS probability0.13%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Reservation-accounting error in Linux 6.9 allows local users to underflow the hugetlb reserved-page count during shared-folio unmapping. __unmap_hugepage_range() adjusts the reservation while a huge-page folio remains mapped by another process because it does not first require a zero mapcount. Triggering requires the folio to be mapped in both a parent and child, with the parent unmapping first; no crash or privilege gain is reported.

The record

CVE
CVE-2026-89593
Published
Sep 11, 2026
Updated
Sep 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
Unavailable
Attack vector
local
Privileges
Unavailable

Timeline

How it unfolded

  1. Sep 11, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 11, 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=6.9
  2. Affected versionversion=df7a6d1f64056aec572162c5d35ed9ff86ece6f3 <0f001491e5a2ec69aa9d5dd6b799e5742245f9ea
  3. Affected versionversion=df7a6d1f64056aec572162c5d35ed9ff86ece6f3 <5120b1e048d48596ffaec1a8412012a91adba73b
  4. Affected versionversion=df7a6d1f64056aec572162c5d35ed9ff86ece6f3 <a3c65af20cceb7f997847727636b4017326f845d

What conditions does exploitation require?

Attack vectorlocal
Required privilegesUnavailable in this record.

What is affected?

The Linux Kernel Organization · Linuxversion=6.9; version=df7a6d1f64056aec572162c5d35ed9ff86ece6f3 <0f001491e5a2ec69aa9d5dd6b799e5742245f9ea; version=df7a6d1f64056aec572162c5d35ed9ff86ece6f3 <5120b1e048d48596ffaec1a8412012a91adba73b; version=df7a6d1f64056aec572162c5d35ed9ff86ece6f3 <a3c65af20cceb7f997847727636b4017326f845d

Published CVSS scores

No CVSS assessment is available in this record.

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
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

No sourced classifications are available.

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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