CVE-2026-68329

Estado: RecibidaAlta (8.8)—

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

iommu/amd: Wait for completion instead of returning early in iommu_completion_wait()

need_sync is a per-IOMMU flag shared by all domains and devices behind that IOMMU. It is set whenever a command is queued with sync == true and cleared when a completion-wait (CWAIT) command is queued. However, a cleared need_sync only means that a covering CWAIT has been queued, not that all previously queued commands have actually completed in hardware.

iommu_completion_wait() read need_sync locklessly and returned early when it was false. This breaks the "block until all previously queued commands have completed" contract in a multi-CPU scenario:

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CPU2 returns without waiting for any sequence number even though its inv-B may not have completed yet (CWAIT(N), queued after inv-B, has not been signaled). CPU2 then proceeds to, for example, free page-table pages while the IOMMU can still walk stale translations, opening a use-after-free window. This is a logical race in the meaning of the flag, not a memory-visibility issue, so barriers alone do not help.

Fix it without losing the optimization of avoiding redundant CWAIT commands: take iommu->lock before testing need_sync, and when it is false do not return early but wait for the last allocated sequence number (cmd_sem_val). Since need_sync == false implies no sync command was queued after the last CWAIT, that CWAIT is FIFO-ordered after every not-yet-completed command, so waiting for its sequence number guarantees all prior commands (possibly queued by another CPU) have completed. The common path with pending work is unchanged and no extra hardware command is issued.

Detalles técnicos trazas, registros y código del informe original

  CPU2: queue inv-B                  => need_sync = true
  CPU1: queue CWAIT(N); need_sync = false; then wait_on_sem(N)
  CPU2: read need_sync == false      => return 0 (no wait!)

CVSS

Versión: 3.1
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Puntuación base: 8.8

Probabilidad de explotación (EPSS)

Probabilidad de explotación en los próximos 30 días: 0.17%
Percentil entre todas las CVEs puntuadas: 6
Fecha de la puntuación: 6/10/2026

EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).

🎯 Técnicas ATT&CK

Cómo se explota esta vulnerabilidad y qué consigue el atacante, en el lenguaje de MITRE ATT&CK.

ExplotaciónT1068 Exploitation for Privilege Escalationprivilege escalation85 %
Impacto principalT1565.001 Stored Data Manipulationimpact75 %
Impacto secundarioT1499.004 Application or System Exploitationimpact70 %

Acceso local sin interacción (AV:L, PR:L, UI:N) permite escalar privilegios mediante race condition en sincronización IOMMU. Impacto: manipulación de memoria (use-after-free) y potencial DoS.

Inferido por nuestro agente de análisis a partir de la descripción oficial, el vector CVSS y la CWE, y comprobado por un supervisor. Puede contener errores.

🛡️ Mitigaciones ATT&CK que cubren estas técnicas

Threat Intelligence Program Restrict File and Directory Permissions Remote Data Storage Filter Network Traffic Execution Prevention Encrypt Sensitive Information

Tecnologías afectadas (1)

⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.

Linux — Linux Kernel^AI

Referencias

JSON original (NVD)

Mostrar

{
  "id": "CVE-2026-68329",
  "cveTags": [],
  "metrics": {
    "cvssMetricV31": [
      {
        "type": "Secondary",
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "cvssData": {
          "scope": "CHANGED",
          "version": "3.1",
          "baseScore": 8.8,
          "attackVector": "LOCAL",
          "baseSeverity": "HIGH",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H",
          "integrityImpact": "HIGH",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "confidentialityImpact": "HIGH"
        },
        "impactScore": 6,
        "exploitabilityScore": 2
      }
    ]
  },
  "affected": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "affectedData": [
        {
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "product": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "815b33fdc279d34ab40a8bfe1866623a4cc5669b",
              "lessThan": "ab7faf5a172ebfdc423ebb3eea4d472740de82f9",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "815b33fdc279d34ab40a8bfe1866623a4cc5669b",
              "lessThan": "93494bd446396c257fb589f59894577e96e406e2",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "815b33fdc279d34ab40a8bfe1866623a4cc5669b",
              "lessThan": "d053eb7e09e10cbdca3fca8b35c1017d438091b2",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "815b33fdc279d34ab40a8bfe1866623a4cc5669b",
              "lessThan": "02f8cefa2ad95ea3754f0cfd6fbae7f866202ccb",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "815b33fdc279d34ab40a8bfe1866623a4cc5669b",
              "lessThan": "1e75a8255f11c81fb07e81e5029cfd75804350a0",
              "versionType": "git"
            }
          ],
          "programFiles": [
            "drivers/iommu/amd/iommu.c"
          ],
          "defaultStatus": "unaffected"
        },
        {
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "product": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "3.0"
            },
            {
              "status": "unaffected",
              "version": "0",
              "lessThan": "3.0",
              "versionType": "semver"
            },
            {
              "status": "unaffected",
              "version": "6.6.148",
              "versionType": "semver",
              "lessThanOrEqual": "6.6.*"
            },
            {
              "status": "unaffected",
              "version": "6.12.101",
              "versionType": "semver",
              "lessThanOrEqual": "6.12.*"
            },
            {
              "status": "unaffected",
              "version": "6.18.42",
              "versionType": "semver",
              "lessThanOrEqual": "6.18.*"
            },
            {
              "status": "unaffected",
              "version": "7.1.6",
              "versionType": "semver",
              "lessThanOrEqual": "7.1.*"
            },
            {
              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix",
              "lessThanOrEqual": "*"
            }
          ],
          "programFiles": [
            "drivers/iommu/amd/iommu.c"
          ],
          "defaultStatus": "affected"
        }
      ]
    }
  ],
  "published": "2026-08-10T13:20:23.160",
  "references": [
    {
      "url": "https://git.kernel.org/stable/c/02f8cefa2ad95ea3754f0cfd6fbae7f866202ccb",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/1e75a8255f11c81fb07e81e5029cfd75804350a0",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/93494bd446396c257fb589f59894577e96e406e2",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/ab7faf5a172ebfdc423ebb3eea4d472740de82f9",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/d053eb7e09e10cbdca3fca8b35c1017d438091b2",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "vulnStatus": "Received",
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\niommu/amd: Wait for completion instead of returning early in iommu_completion_wait()\n\nneed_sync is a per-IOMMU flag shared by all domains and devices behind\nthat IOMMU. It is set whenever a command is queued with sync == true and\ncleared when a completion-wait (CWAIT) command is queued. However, a\ncleared need_sync only means that a covering CWAIT has been queued, not\nthat all previously queued commands have actually completed in hardware.\n\niommu_completion_wait() read need_sync locklessly and returned early\nwhen it was false. This breaks the \"block until all previously queued\ncommands have completed\" contract in a multi-CPU scenario:\n\n  CPU2: queue inv-B                  => need_sync = true\n  CPU1: queue CWAIT(N); need_sync = false; then wait_on_sem(N)\n  CPU2: read need_sync == false      => return 0 (no wait!)\n\nCPU2 returns without waiting for any sequence number even though its\ninv-B may not have completed yet (CWAIT(N), queued after inv-B, has not\nbeen signaled). CPU2 then proceeds to, for example, free page-table\npages while the IOMMU can still walk stale translations, opening a\nuse-after-free window. This is a logical race in the meaning of the\nflag, not a memory-visibility issue, so barriers alone do not help.\n\nFix it without losing the optimization of avoiding redundant CWAIT\ncommands: take iommu->lock before testing need_sync, and when it is\nfalse do not return early but wait for the last allocated sequence\nnumber (cmd_sem_val). Since need_sync == false implies no sync command\nwas queued after the last CWAIT, that CWAIT is FIFO-ordered after every\nnot-yet-completed command, so waiting for its sequence number guarantees\nall prior commands (possibly queued by another CPU) have completed. The\ncommon path with pending work is unchanged and no extra hardware command\nis issued."
    }
  ],
  "lastModified": "2026-08-17T06:17:40.947",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}