In the Linux kernel, the following vulnerability has been resolved: hugetlb: only adjust reservation during unmapping if mapcount is 0 Since… (CVE-2026-89593)
A vulnerability in the Linux kernel's hugetlb subsystem was resolved by ensuring reservation adjustments during unmapping only occur if the mapcount is zero. The issue involved an underflow of the reserved count when a folio mapped in both a parent and child process was unmapped first by the parent, causing incorrect reservation adjustment. The fix modifies __unmap_hugepage_range() to check the mapcount before adjusting reservations.
AI Analysis
Technical Summary
The Linux kernel vulnerability CVE-2026-89593 concerns the hugetlb subsystem's handling of reservation adjustments during unmapping of huge pages. Since commit df7a6d1f6405, __unmap_hugepage_range could adjust reservations even when a folio was mapped in both a parent and child process. If the parent unmapped the range first, this caused an underflow in the reserved count. The count was restored only after the child unmapped the range. The patch changes __unmap_hugepage_range() to verify that the mapcount is zero before adjusting the reservation, preventing the underflow condition.
Potential Impact
The vulnerability could cause an underflow of the reserved count in the hugetlb subsystem during unmapping operations involving shared mappings between parent and child processes. This could potentially lead to incorrect memory reservation accounting in the kernel. No known exploits in the wild have been reported.
Mitigation Recommendations
A fix has been implemented in the Linux kernel source code to address this issue by adding a mapcount check before adjusting reservations during unmapping. Users should apply the official kernel updates that include this patch. Patch status is not explicitly confirmed in the provided data; check the vendor or kernel mailing list advisories for the exact fixed versions and update accordingly.
In the Linux kernel, the following vulnerability has been resolved: hugetlb: only adjust reservation during unmapping if mapcount is 0 Since… (CVE-2026-89593)
Description
A vulnerability in the Linux kernel's hugetlb subsystem was resolved by ensuring reservation adjustments during unmapping only occur if the mapcount is zero. The issue involved an underflow of the reserved count when a folio mapped in both a parent and child process was unmapped first by the parent, causing incorrect reservation adjustment. The fix modifies __unmap_hugepage_range() to check the mapcount before adjusting reservations.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The Linux kernel vulnerability CVE-2026-89593 concerns the hugetlb subsystem's handling of reservation adjustments during unmapping of huge pages. Since commit df7a6d1f6405, __unmap_hugepage_range could adjust reservations even when a folio was mapped in both a parent and child process. If the parent unmapped the range first, this caused an underflow in the reserved count. The count was restored only after the child unmapped the range. The patch changes __unmap_hugepage_range() to verify that the mapcount is zero before adjusting the reservation, preventing the underflow condition.
Potential Impact
The vulnerability could cause an underflow of the reserved count in the hugetlb subsystem during unmapping operations involving shared mappings between parent and child processes. This could potentially lead to incorrect memory reservation accounting in the kernel. No known exploits in the wild have been reported.
Mitigation Recommendations
A fix has been implemented in the Linux kernel source code to address this issue by adding a mapcount check before adjusting reservations during unmapping. Users should apply the official kernel updates that include this patch. Patch status is not explicitly confirmed in the provided data; check the vendor or kernel mailing list advisories for the exact fixed versions and update accordingly.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- GHSA-xm38-wfrw-x5q7
- Osv Schema Version
- 1.4.0
- Aliases
- ["CVE-2026-89593"]
Threat ID: 6aa4a00b55bf5e2cf5a86669
Added to database: 09/12/2026, 00:42:51 UTC
Last enriched: 09/12/2026, 01:02:05 UTC
Last updated: 09/12/2026, 01:02:05 UTC
Views: 2
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