Service interruption via non-LIFO PTE unmapping
Published Oct 1, 2025 · Updated May 11, 2026
Improper PTE unmapping in Linux 6.8 through 6.12.45 and 6.13 through 6.16.5 allows local users to interrupt service on 32-bit ARM. The move_pages_pte() path in mm/userfaultfd.c maps dst_pte and then src_pte with kmap_local_page(), but unmaps them in the same order instead of the required LIFO order. Exploitation requires low-privilege local access and a 32-bit ARM kernel built with CONFIG_HIGHPTE; the ordering violation triggers a high-memory unmap warning and disrupts kernel availability.
Summary
What happened
Improper PTE unmapping in Linux 6.8 through 6.12.45 and 6.13 through 6.16.5 allows local users to interrupt service on 32-bit ARM. The move_pages_pte() path in mm/userfaultfd.c maps dst_pte and then src_pte with kmap_local_page(), but unmaps them in the same order instead of the required LIFO order. Exploitation requires low-privilege local access and a 32-bit ARM kernel built with CONFIG_HIGHPTE; the ordering violation triggers a high-memory unmap warning and disrupts kernel availability.
The record
- CVE
- CVE-2025-39899
- Published
- Oct 1, 2025
- Updated
- May 11, 2026
- Vendor
- The Linux Kernel Organization
- Product
- Linux
- Classifications
- T1499.004
- Attack vector
- local
- Privileges
- authenticated
Timeline
How it unfolded
- Oct 1, 2025CVE publishedPublication date reported by the CVE source.
- May 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?
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- Affected versionversion=6.8
- Affected versionversion=adef440691bab824e39c1b17382322d195e1fab0 <9614d8bee66387501f48718fa306e17f2aa3f2f3
- Affected versionversion=adef440691bab824e39c1b17382322d195e1fab0 <b051f707018967ea8f697d790a1ed8c443f63812
- Affected versionversion=adef440691bab824e39c1b17382322d195e1fab0 <bd1ee62759d0bd4d6b909731c076c230ac89d61e
What conditions does exploitation require?
What is affected?
Attacks
What attackers are doing with it
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Weakness, pattern, technique
Public exploit references
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