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CVE-2026-53396

Estado: AnalizadaAlta (7.1)—

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

nfsd: fix posix_acl leak and ignored error in nfsd4_create_file

nfsd4_create_file() has two bugs in its ACL handling:

The return value of nfsd4_acl_to_attr() is silently discarded. When the NFSv4-to-POSIX ACL conversion fails (e.g., -EINVAL for unsupported ACE types), the file is created without any ACL and the client receives NFS4_OK. This violates RFC 7530/8881 which require the server to reject unsupported attributes on CREATE.

When start_creating() fails after ACL attributes have been populated in attrs (either via nfsd4_acl_to_attr or via ownership transfer from open->op_dpacl/op_pacl), the function jumps to out_write which skips nfsd_attrs_free().

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The posix_acl allocations are leaked. A client can trigger this repeatedly with OPEN(CREATE), ACL attributes, and an invalid filename (e.g., longer than NAME_MAX).

Fix both by capturing the nfsd4_acl_to_attr() return value and by changing the early error paths to jump to out instead of out_write. Initialize child to ERR_PTR(-EINVAL) so that end_creating() is safe to call even if start_creating() was never reached.

CVSS

Probabilidad de explotación (EPSS)

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.

AV:N/PR:L/AC:L con impacto DoS (A:H) y posible escalada tras manipulación de ACLs en kernel NFS remoto; fuga de memoria y rechazo de validación permite denegación de servicio.

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 ProgramApplication Isolation and SandboxingExploit ProtectionUpdate SoftwareVulnerability ScanningPrivileged Account Management

Tecnologías afectadas (1)

Linux — Linux Kernel

CWE

Referencias

JSON original (NVD)

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{
  "id": "CVE-2026-53396",
  "cveTags": [],
  "metrics": {
    "cvssMetricV31": [
      {
        "type": "Secondary",
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 7.1,
          "attackVector": "NETWORK",
          "baseSeverity": "HIGH",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H",
          "integrityImpact": "LOW",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "confidentialityImpact": "NONE"
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        "impactScore": 4.2,
        "exploitabilityScore": 2.8
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              "versionType": "git"
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          "programFiles": [
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        {
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          "programFiles": [
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        }
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  ],
  "published": "2026-07-19T12:16:50.693",
  "references": [
    {
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      "tags": [
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      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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    {
      "url": "https://git.kernel.org/stable/c/24c975bbdd564d7d0ad90294bfa69729830345de",
      "tags": [
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      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "type": "Primary",
      "source": "nvd@nist.gov",
      "description": [
        {
          "lang": "en",
          "value": "CWE-401"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: fix posix_acl leak and ignored error in nfsd4_create_file\n\nnfsd4_create_file() has two bugs in its ACL handling:\n\nThe return value of nfsd4_acl_to_attr() is silently discarded.  When\nthe NFSv4-to-POSIX ACL conversion fails (e.g., -EINVAL for\nunsupported ACE types), the file is created without any ACL and the\nclient receives NFS4_OK.  This violates RFC 7530/8881 which require\nthe server to reject unsupported attributes on CREATE.\n\nWhen start_creating() fails after ACL attributes have been populated\nin attrs (either via nfsd4_acl_to_attr or via ownership transfer from\nopen->op_dpacl/op_pacl), the function jumps to out_write which skips\nnfsd_attrs_free().  The posix_acl allocations are leaked.  A client\ncan trigger this repeatedly with OPEN(CREATE), ACL attributes, and an\ninvalid filename (e.g., longer than NAME_MAX).\n\nFix both by capturing the nfsd4_acl_to_attr() return value and by\nchanging the early error paths to jump to out instead of out_write.\nInitialize child to ERR_PTR(-EINVAL) so that end_creating() is safe\nto call even if start_creating() was never reached."
    }
  ],
  "lastModified": "2026-08-17T05:17:14.153",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "9526B150-E2B3-4C6F-8AE5-1AF92B75AD9E",
              "versionEndExcluding": "7.1.3",
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          ],
          "operator": "OR"
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  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}