CVE-2026-43486 (GCVE-0-2026-43486)

Vulnerability from cvelistv5 – Published: 2026-05-13 15:08 – Updated: 2026-05-13 15:08
VLAI
Title
arm64: contpte: fix set_access_flags() no-op check for SMMU/ATS faults
Summary
In the Linux kernel, the following vulnerability has been resolved: arm64: contpte: fix set_access_flags() no-op check for SMMU/ATS faults contpte_ptep_set_access_flags() compared the gathered ptep_get() value against the requested entry to detect no-ops. ptep_get() ORs AF/dirty from all sub-PTEs in the CONT block, so a dirty sibling can make the target appear already-dirty. When the gathered value matches entry, the function returns 0 even though the target sub-PTE still has PTE_RDONLY set in hardware. For a CPU with FEAT_HAFDBS this gathered view is fine, since hardware may set AF/dirty on any sub-PTE and CPU TLB behavior is effectively gathered across the CONT range. But page-table walkers that evaluate each descriptor individually (e.g. a CPU without DBM support, or an SMMU without HTTU, or with HA/HD disabled in CD.TCR) can keep faulting on the unchanged target sub-PTE, causing an infinite fault loop. Gathering can therefore cause false no-ops when only a sibling has been updated: - write faults: target still has PTE_RDONLY (needs PTE_RDONLY cleared) - read faults: target still lacks PTE_AF Fix by checking each sub-PTE against the requested AF/dirty/write state (the same bits consumed by __ptep_set_access_flags()), using raw per-PTE values rather than the gathered ptep_get() view, before returning no-op. Keep using the raw target PTE for the write-bit unfold decision. Per Arm ARM (DDI 0487) D8.7.1 ("The Contiguous bit"), any sub-PTE in a CONT range may become the effective cached translation and software must maintain consistent attributes across the range.
Severity
5.5 (Medium)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 6639 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 4602e5757bcceb231c3a13c36c373ad4a750eddb , < 05d239f2c95e66e27e7fb4e99ee07eb56e3e34b0 (git)
Affected: 4602e5757bcceb231c3a13c36c373ad4a750eddb , < 6f92a7a8b48a523f910ef25dd83808710724f59b (git)
Affected: 4602e5757bcceb231c3a13c36c373ad4a750eddb , < 09d620555e59768776090073a2c59d2bc8506eb3 (git)
Affected: 4602e5757bcceb231c3a13c36c373ad4a750eddb , < 97c5550b763171dbef61e6239cab372b9f9cd4a2 (git)
guessed Create a notification for this product.
Linux Linux Affected: 6.9
Unaffected: 0 , < 6.9 (semver)
Unaffected: 6.12.78 , ≤ 6.12.* (semver)
Unaffected: 6.18.19 , ≤ 6.18.* (semver)
Unaffected: 6.19.9 , ≤ 6.19.* (semver)
Unaffected: 7.0 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
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      "cve": "CVE-2026-43486",
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      "product_status:known_affected": "1",
      "product_status:known_not_affected": "199",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: arm64: contpte: fix set_access_flags() no-op check for SMMU/ATS faults",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-43486.json",
      "version": "3"
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}



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