GHSA-H9HG-3WV2-X6J7

Vulnerability from github – Published: 2026-07-19 18:31 – Updated: 2026-07-20 15:31
VLAI
Details

In the Linux kernel, the following vulnerability has been resolved:

arm64: tlb: Flush walk cache when unsharing PMD tables

When huge_pmd_unshare() is called to unshare a PMD table, the tlb_unshare_pmd_ptdesc() function sets tlb->unshared_tables=true but the aarch64 tlb_flush() only checked tlb->freed_tables to determine whether to use TLBF_NONE (vae1is, invalidates walk cache) or TLBF_NOWALKCACHE (vale1is, leaf-only).

This caused the stale PMD page table entry to remain in the walk cache after unshare, potentially leading to incorrect page table walks.

Fix by including unshared_tables in the check, so that when unsharing tables, TLBF_NONE is used and the walk cache is properly invalidated.

Here is the detailed distinction between vae1is and vale1is:

Instruction Combination Actual Invalidation Scope
VAE1IS + TTL=0 All entries at all levels (full invalidation)
VAE1IS + TTL=2 (L2) Non-leaf at Level 0/1 + leaf at Level 2
VALE1IS + TTL=0 Leaf entries at all levels (non-leaf not cleared)
VALE1IS + TTL=2 (L2) Leaf entry at Level 2 only
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
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{
  "affected": [],
  "aliases": [
    "CVE-2026-63875"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-07-19T16:17:04Z",
    "severity": "HIGH"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\narm64: tlb: Flush walk cache when unsharing PMD tables\n\nWhen huge_pmd_unshare() is called to unshare a PMD table, the\ntlb_unshare_pmd_ptdesc() function sets tlb-\u003eunshared_tables=true\nbut the aarch64 tlb_flush() only checked tlb-\u003efreed_tables to\ndetermine whether to use TLBF_NONE (vae1is, invalidates walk\ncache) or TLBF_NOWALKCACHE (vale1is, leaf-only).\n\nThis caused the stale PMD page table entry to remain in the walk cache\nafter unshare, potentially leading to incorrect page table walks.\n\nFix by including unshared_tables in the check, so that when\nunsharing tables, TLBF_NONE is used and the walk cache is properly\ninvalidated.\n\nHere is the detailed distinction between vae1is and vale1is:\n\n| Instruction Combination  | Actual Invalidation Scope                         |\n| ------------------------ | --------------------------------------------------|\n| `VAE1IS`  + TTL=`0`      | All entries at all levels (full invalidation)     |\n| `VAE1IS`  + TTL=`2` (L2) | Non-leaf at Level 0/1 + leaf at Level 2           |\n| `VALE1IS` + TTL=`0`      | Leaf entries at all levels (non-leaf not cleared) |\n| `VALE1IS` + TTL=`2` (L2) | Leaf entry at Level 2 only                        |",
  "id": "GHSA-h9hg-3wv2-x6j7",
  "modified": "2026-07-20T15:31:49Z",
  "published": "2026-07-19T18:31:43Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-63875"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/0199c9d57861f17b556b6cba1f765c7cce79745b"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/47490bbb05c8c0e09cc3cfd237d8934ffc340583"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/48125cd9c55cbe297b59fd1f9bda48b0960bd181"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/8ca7284da0e67b3e71d90ec17f08286774245ad9"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/c2ff4764e03e7a8d758352f4aceb8fe1be6ac971"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/d766a49d9b55705c4737cd8bb5d3faa2d31330fd"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/dced308d7d6a0de1c09d2058f38f1aaaf5cbb914"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/fe93e907b1af03cc229a80aa64a570a103d2b279"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}



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