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CVE-2026-74485

Estado: RecibidaAlta (7.1)—

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

binfmt_misc: reject a flag character as the field delimiter

The registration string starts with a user chosen delimiter that separates the individual fields. So that the field parsers terminate even on a truncated string create_entry() pads the buffer with that same delimiter:

Most fields are scanned for the delimiter with strchr()/scanarg() and happily stop on the padding. The flags field is different: instead of scanning for the delimiter check_special_flags() consumes the flag characters 'P', 'O', 'C' and 'F' and stops at the first byte that is none of them, relying on the trailing delimiter to end the scan.

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If the delimiter is itself a flag character the padding no longer acts as a terminator. The scan swallows all eight padding bytes and keeps reading past the end of the allocation until it hits a byte that is not a flag character. For example registering

with 'P' as the delimiter (name "a", type extension, magic "x", interpreter "i", empty flags) leaves the flag scan running off the end of the buffer. The registration is rejected in the end because the parser does not stop exactly at buf + count, but only after the out of bounds read has already happened. With an unlucky allocation layout the scan can walk into an unmapped page; under KASAN it is reported as a slab out of bounds read. binfmt_misc mounts are available to unprivileged users in a user namespace so the read is reachable without privileges.

Reject a delimiter that is one of the flag characters up front. Such a registration was always rejected anyway, only after the out of bounds read, so no valid registration string changes meaning.

Detalles técnicos trazas, registros y código del informe original
	memset(buf + count, del, 8);

	PaPEPPxPPiP

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.

Acceso local (AV:L, PR:L) sin interacción: escalada de privilegios mediante lectura de memoria fuera de límites en binfmt_misc accesible a usuarios sin privilegios en namespaces.

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 ProgramExecution PreventionApplication Isolation and SandboxingExploit ProtectionUpdate SoftwareData Loss Prevention

Tecnologías afectadas (1)

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

Linux — Linux KernelAI

Referencias

JSON original (NVD)

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{
  "id": "CVE-2026-74485",
  "cveTags": [],
  "metrics": {
    "cvssMetricV31": [
      {
        "type": "Secondary",
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 7.1,
          "attackVector": "LOCAL",
          "baseSeverity": "HIGH",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H",
          "integrityImpact": "NONE",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "confidentialityImpact": "HIGH"
        },
        "impactScore": 5.2,
        "exploitabilityScore": 1.8
      }
    ]
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  "affected": [
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      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "affectedData": [
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          "vendor": "Linux",
          "product": "Linux",
          "versions": [
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              "status": "affected",
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          ],
          "programFiles": [
            "fs/binfmt_misc.c"
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          "defaultStatus": "unaffected"
        },
        {
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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              "version": "2.6.12"
            },
            {
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              "version": "0",
              "lessThan": "2.6.12",
              "versionType": "semver"
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            {
              "status": "unaffected",
              "version": "5.10.265",
              "versionType": "semver",
              "lessThanOrEqual": "5.10.*"
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            {
              "status": "unaffected",
              "version": "5.15.216",
              "versionType": "semver",
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            },
            {
              "status": "unaffected",
              "version": "6.1.183",
              "versionType": "semver",
              "lessThanOrEqual": "6.1.*"
            },
            {
              "status": "unaffected",
              "version": "6.6.151",
              "versionType": "semver",
              "lessThanOrEqual": "6.6.*"
            },
            {
              "status": "unaffected",
              "version": "6.12.103",
              "versionType": "semver",
              "lessThanOrEqual": "6.12.*"
            },
            {
              "status": "unaffected",
              "version": "6.18.44",
              "versionType": "semver",
              "lessThanOrEqual": "6.18.*"
            },
            {
              "status": "unaffected",
              "version": "7.1.8",
              "versionType": "semver",
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            },
            {
              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix",
              "lessThanOrEqual": "*"
            }
          ],
          "programFiles": [
            "fs/binfmt_misc.c"
          ],
          "defaultStatus": "affected"
        }
      ]
    }
  ],
  "published": "2026-08-15T13:17:53.380",
  "references": [
    {
      "url": "https://git.kernel.org/stable/c/1819f82dee766c58295ecaacdac02cdf6837d7a4",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/1853e95c9bfe69ef1dd862b3f551e68f4a1b76cc",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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    {
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      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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    {
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      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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    {
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      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/b29e3c1f375c1296362d219ff38bceddf2d2a88a",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "vulnStatus": "Received",
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbinfmt_misc: reject a flag character as the field delimiter\n\nThe registration string starts with a user chosen delimiter that\nseparates the individual fields. So that the field parsers terminate\neven on a truncated string create_entry() pads the buffer with that\nsame delimiter:\n\n\tmemset(buf + count, del, 8);\n\nMost fields are scanned for the delimiter with strchr()/scanarg() and\nhappily stop on the padding. The flags field is different: instead of\nscanning for the delimiter check_special_flags() consumes the flag\ncharacters 'P', 'O', 'C' and 'F' and stops at the first byte that is\nnone of them, relying on the trailing delimiter to end the scan.\n\nIf the delimiter is itself a flag character the padding no longer acts\nas a terminator. The scan swallows all eight padding bytes and keeps\nreading past the end of the allocation until it hits a byte that is\nnot a flag character. For example registering\n\n\tPaPEPPxPPiP\n\nwith 'P' as the delimiter (name \"a\", type extension, magic \"x\",\ninterpreter \"i\", empty flags) leaves the flag scan running off the end\nof the buffer. The registration is rejected in the end because the\nparser does not stop exactly at buf + count, but only after the out of\nbounds read has already happened. With an unlucky allocation layout the\nscan can walk into an unmapped page; under KASAN it is reported as a\nslab out of bounds read. binfmt_misc mounts are available to\nunprivileged users in a user namespace so the read is reachable without\nprivileges.\n\nReject a delimiter that is one of the flag characters up front. Such a\nregistration was always rejected anyway, only after the out of bounds\nread, so no valid registration string changes meaning."
    }
  ],
  "lastModified": "2026-08-19T17:21:05.660",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}