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CVE-2026-23248

Estado: AnalizadaAlta (7.8)—

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

perf/core: Fix refcount bug and potential UAF in perf_mmap

Syzkaller reported a refcount_t: addition on 0; use-after-free warning in perf_mmap.

The issue is caused by a race condition between a failing mmap() setup and a concurrent mmap() on a dependent event (e.g., using output redirection).

In perf_mmap(), the ring_buffer (rb) is allocated and assigned to event->rb with the mmap_mutex held. The mutex is then released to perform map_range().

If map_range() fails, perf_mmap_close() is called to clean up. However, since the mutex was dropped, another thread attaching to this event (via inherited events or output redirection) can acquire the mutex, observe the valid event->rb pointer, and attempt to increment its reference count. If the cleanup path has already dropped the reference count to zero, this results in a use-after-free or refcount saturation warning.

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Fix this by extending the scope of mmap_mutex to cover the map_range() call. This ensures that the ring buffer initialization and mapping (or cleanup on failure) happens atomically effectively, preventing other threads from accessing a half-initialized or dying ring buffer.

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) sin interacción de usuario; vulnerabilidad de race condition en perf_mmap que permite escalada de privilegios mediante UAF (CWE-416), con posible ejecución de código en contexto elevado.

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

Execution PreventionThreat Intelligence ProgramRestrict Web-Based ContentPrivileged Account ManagementLimit Software InstallationBehavior Prevention on Endpoint

Tecnologías afectadas (1)

Linux — Linux Kernel

CWE

Referencias

JSON original (NVD)

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{
  "id": "CVE-2026-23248",
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        "type": "Secondary",
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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          "version": "3.1",
          "baseScore": 7.8,
          "attackVector": "LOCAL",
          "baseSeverity": "HIGH",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
          "integrityImpact": "HIGH",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
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              "versionType": "semver"
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              "version": "6.18.17",
              "versionType": "semver",
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  "published": "2026-03-18T11:16:16.863",
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  "vulnStatus": "Analyzed",
  "weaknesses": [
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      "type": "Primary",
      "source": "nvd@nist.gov",
      "description": [
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          "lang": "en",
          "value": "CWE-416"
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      ]
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  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nperf/core: Fix refcount bug and potential UAF in perf_mmap\n\nSyzkaller reported a refcount_t: addition on 0; use-after-free warning\nin perf_mmap.\n\nThe issue is caused by a race condition between a failing mmap() setup\nand a concurrent mmap() on a dependent event (e.g., using output\nredirection).\n\nIn perf_mmap(), the ring_buffer (rb) is allocated and assigned to\nevent->rb with the mmap_mutex held. The mutex is then released to\nperform map_range().\n\nIf map_range() fails, perf_mmap_close() is called to clean up.\nHowever, since the mutex was dropped, another thread attaching to\nthis event (via inherited events or output redirection) can acquire\nthe mutex, observe the valid event->rb pointer, and attempt to\nincrement its reference count. If the cleanup path has already\ndropped the reference count to zero, this results in a\nuse-after-free or refcount saturation warning.\n\nFix this by extending the scope of mmap_mutex to cover the\nmap_range() call. This ensures that the ring buffer initialization\nand mapping (or cleanup on failure) happens atomically effectively,\npreventing other threads from accessing a half-initialized or\ndying ring buffer."
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nperf/core: Corrección de error de conteo de referencias y potencial UAF en perf_mmap\n\nSyzkaller informó una advertencia de refcount_t: adición en 0; uso después de liberación en perf_mmap.\n\nEl problema es causado por una condición de carrera entre una configuración de mmap() fallida y un mmap() concurrente en un evento dependiente (por ejemplo, usando redirección de salida).\n\nEn perf_mmap(), el ring_buffer (rb) se asigna y se establece en event->rb con el mmap_mutex retenido. El mutex es entonces liberado para realizar map_range().\n\nSi map_range() falla, se llama a perf_mmap_close() para limpiar. Sin embargo, dado que el mutex fue liberado, otro hilo que se adjunta a este evento (a través de eventos heredados o redirección de salida) puede adquirir el mutex, observar el puntero event->rb válido e intentar incrementar su conteo de referencias. Si la ruta de limpieza ya ha reducido el conteo de referencias a cero, esto resulta en un uso después de liberación o una advertencia de saturación de conteo de referencias.\n\nEsto se corrige al extender el alcance de mmap_mutex para cubrir la llamada a map_range(). Esto asegura que la inicialización y el mapeo del búfer de anillo (o la limpieza en caso de fallo) ocurra de manera atómica y efectiva, evitando que otros hilos accedan a un búfer de anillo medio inicializado o en proceso de terminación."
    }
  ],
  "lastModified": "2026-06-17T10:21:11.000",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
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              "versionEndExcluding": "6.18.17",
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}