CVE-2026-43497

Estado: AnalizadaAlta (7.3)—

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

fbdev: udlfb: add vm_ops to dlfb_ops_mmap to prevent use-after-free

dlfb_ops_mmap() uses remap_pfn_range() to map vmalloc framebuffer pages to userspace but sets no vm_ops on the VMA. This means the kernel cannot track active mmaps. When dlfb_realloc_framebuffer() replaces the backing buffer via FBIOPUT_VSCREENINFO, existing mmap PTEs are not invalidated. On USB disconnect, dlfb_ops_destroy() calls vfree() on the old pages while userspace PTEs still reference them, resulting in a use-after-free: the process retains read/write access to freed kernel pages.

Leer descripción completaMostrar menos

Add vm_operations_struct with open/close callbacks that maintain an atomic mmap_count on struct dlfb_data. In dlfb_realloc_framebuffer(), check mmap_count and return -EBUSY if the buffer is currently mapped, preventing buffer replacement while userspace holds stale PTEs.

Tested with PoC using dummy_hcd + raw_gadget USB device emulation.

CVSS

Versión: 3.1
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H
Puntuación base: 7.3

Probabilidad de explotación (EPSS)

Probabilidad de explotación en los próximos 30 días: 0.17%
Percentil entre todas las CVEs puntuadas: 5
Fecha de la puntuación: 5/10/2026

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.

ExplotaciónT1203 Exploitation for Client Executionexecution75 %
Impacto principalT1059 Command and Scripting Interpreterexecution60 %
Impacto secundarioT1565 Data Manipulationimpact70 %

AV:L + UI:R + ejecución arbitraria en contexto del kernel: requiere interacción del usuario (abrir aplicación con framebuffer mapeado). Use-after-free permite leer/escribir páginas kernel liberadas (T1565 por corrupción de memoria).

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

Restrict Web-Based Content Restrict File and Directory Permissions Privileged Account Management Remote Data Storage Network Segmentation Limit Software Installation

Tecnologías afectadas (1)

Linux — Linux Kernel

CWE

CWE-416

Referencias

JSON original (NVD)

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      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nfbdev: udlfb: add vm_ops to dlfb_ops_mmap to prevent use-after-free\n\ndlfb_ops_mmap() uses remap_pfn_range() to map vmalloc framebuffer pages\nto userspace but sets no vm_ops on the VMA. This means the kernel cannot\ntrack active mmaps. When dlfb_realloc_framebuffer() replaces the backing\nbuffer via FBIOPUT_VSCREENINFO, existing mmap PTEs are not invalidated.\nOn USB disconnect, dlfb_ops_destroy() calls vfree() on the old pages\nwhile userspace PTEs still reference them, resulting in a use-after-free:\nthe process retains read/write access to freed kernel pages.\n\nAdd vm_operations_struct with open/close callbacks that maintain an\natomic mmap_count on struct dlfb_data. In dlfb_realloc_framebuffer(),\ncheck mmap_count and return -EBUSY if the buffer is currently mapped,\npreventing buffer replacement while userspace holds stale PTEs.\n\nTested with PoC using dummy_hcd + raw_gadget USB device emulation."
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      "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nfbdev: udlfb: añadir vm_ops a dlfb_ops_mmap para prevenir el uso después de liberación\n\ndlfb_ops_mmap() utiliza remap_pfn_range() para mapear páginas de framebuffer de vmalloc al espacio de usuario, pero no establece vm_ops en el VMA. Esto significa que el kernel no puede rastrear mmaps activos. Cuando dlfb_realloc_framebuffer() reemplaza el búfer de respaldo a través de FBIOPUT_VSCREENINFO, los PTEs de mmap existentes no se invalidan. Al desconectar el USB, dlfb_ops_destroy() llama a vfree() en las páginas antiguas mientras los PTEs del espacio de usuario aún las referencian, lo que resulta en un uso después de liberación: el proceso retiene acceso de lectura/escritura a páginas del kernel liberadas.\n\nAñadir vm_operations_struct con callbacks de apertura/cierre que mantienen un mmap_count atómico en la estructura dlfb_data. En dlfb_realloc_framebuffer(), comprobar mmap_count y devolver -EBUSY si el búfer está actualmente mapeado, lo que previene el reemplazo del búfer mientras el espacio de usuario mantiene PTEs obsoletos.\n\nProbado con PoC utilizando emulación de dispositivo USB dummy_hcd + raw_gadget."
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