hugetlb: only adjust reservation during unmapping if mapcount is 0 (CVE-2026-89593) | HOL Guard CVE

Unknown severity · Source severity not reportedCVE-2026-89593

hugetlb: only adjust reservation during unmapping if mapcount is 0

Answer in brief

CVE-2026-89593 records a Unknown severity vulnerability in hugetlb: only adjust reservation during unmapping if mapcount is 0. The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Sep 11, 2026Updated Sep 11, 2026Source checked Sep 11, 2026First seen by HOL Sep 11, 2026Material review Sep 11, 2026

Upstream Advisory

Key facts

Risk: Unknown severitySource severity not reported
Exploitation: Not marked as known exploited
Affected software: 2 mapped packages or products
Fix availability: Available

Why this deserves its current priority

A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
Linux/Linuxgeneric	>=df7a6d1f64056aec572162c5d35ed9ff86ece6f3 <a3c65af20cceb7f997847727636b4017326f845d \|\| >=df7a6d1f64056aec572162c5d35ed9ff86ece6f3 <0f001491e5a2ec69aa9d5dd6b799e5742245f9ea \|\| >=df7a6d1f64056aec572162c5d35ed9ff86ece6f3 <5120b1e048d48596ffaec1a8412012a91adba73b	a3c65af20cceb7f997847727636b4017326f845d, 0f001491e5a2ec69aa9d5dd6b799e5742245f9ea, 5120b1e048d48596ffaec1a8412012a91adba73b
Linux/Linuxgeneric	6.9	Not reported

Recommended response

Check inventory. Check lockfiles and deployed manifests for Linux/Linux, Linux/Linux.
Review the reported fix. Update Linux/Linux to a3c65af20cceb7f997847727636b4017326f845d if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Sep 11, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 11, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 11, 2026

Sources and claim methodology

Upstream source description

In the Linux kernel, the following vulnerability has been resolved: hugetlb: only adjust reservation during unmapping if mapcount is 0 Since df7a6d1f6405, __unmap_hugepage_range can adjust reservations. In the case of folio mapped in both a parent and a child, if the parent unmaps the range first, the reservation adjustment will result in an underflow of the reserved count. Once the child unmaps the range, the count is restored. Change __unmap_hugepage_range() to check the mapcount before adjusting the reservation.

Quoted source text, attributed separately from HOL analysis.