Kernel crash via stale page-count reuse
Published Jul 19, 2026 · Updated Jul 19, 2026
Reference-count corruption in Linux Kernel allows local users to crash the kernel through crafted memory reclaim involving lazy-free folios. In try_to_unmap_one(), nr_pages is not reset for each pvmw iteration, so a count from folio_unmap_pte_batch() is reused for a device-exclusive PTE and corrupts the folio refcount and mapcount. Reachability requires a local low-privilege process, DEVICE_PRIVATE and THP support, access to a GPU render node or hmm_dmirror, and control of lazy-free folio reclaim.
Summary
What happened
Reference-count corruption in Linux Kernel allows local users to crash the kernel through crafted memory reclaim involving lazy-free folios. In try_to_unmap_one(), nr_pages is not reset for each pvmw iteration, so a count from folio_unmap_pte_batch() is reused for a device-exclusive PTE and corrupts the folio refcount and mapcount. Reachability requires a local low-privilege process, DEVICE_PRIVATE and THP support, access to a GPU render node or hmm_dmirror, and control of lazy-free folio reclaim.
The record
- CVE
- CVE-2026-63950
- Published
- Jul 19, 2026
- Updated
- Jul 19, 2026
- Vendor
- The Linux Kernel Organization
- Product
- Linux Kernel
- Classifications
- T1499.004
- Attack vector
- local
- Privileges
- authenticated
Timeline
How it unfolded
- Jul 19, 2026CVE publishedPublication date reported by the CVE source.
- Jul 19, 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.
- Affected versionversion=354dffd29575cdf13154e8fb787322354aa9efc4 <0fcc34d0d8fefca4fea349e45c10e3a3d90350eb
- Affected versionversion=354dffd29575cdf13154e8fb787322354aa9efc4 <3f8968e9cbf95d5d87d32218906cab0b9b9eddbe
- Affected versionversion=354dffd29575cdf13154e8fb787322354aa9efc4 <f611db9b771b2b6775357555d2517af044fca4f0
- Affected versionversion=6.15
What conditions does exploitation require?
What is affected?
Published CVSS scores
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Attacks
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Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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