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CVE-2025-38685

Full vulnerability record from the local CVENow database.

Description

In the Linux kernel, the following vulnerability has been resolved: fbdev: Fix vmalloc out-of-bounds write in fast_imageblit This issue triggers when a userspace program does an ioctl FBIOPUT_CON2FBMAP by passing console number and frame buffer number. Ideally this maps console to frame buffer and updates the screen if console is visible. As part of mapping it has to do resize of console according to frame buffer info. if this resize fails and returns from vc_do_resize() and continues further. At this point console and new frame buffer are mapped and sets display vars. Despite failure still it continue to proceed updating the screen at later stages where vc_data is related to previous frame buffer and frame buffer info and display vars are mapped to new frame buffer and eventully leading to out-of-bounds write in fast_imageblit(). This bheviour is excepted only when fg_console is equal to requested console which is a visible console and updates screen with invalid struct references in fbcon_putcs().

Severity
HIGH
CVSS score
7.8 (v3.1)
Vulnerability status
Modified
Source identifier
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Published
2025-09-04 16:15:36.397000
Last modified
2026-10-19 21:10:00.160000
View original CVE JSON 
{
  "id": "CVE-2025-38685",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "published": "2025-09-04T16:15:36.397",
  "lastModified": "2026-10-19T21:10:00.160",
  "vulnStatus": "Modified",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nfbdev: Fix vmalloc out-of-bounds write in fast_imageblit\n\nThis issue triggers when a userspace program does an ioctl\nFBIOPUT_CON2FBMAP by passing console number and frame buffer number.\nIdeally this maps console to frame buffer and updates the screen if\nconsole is visible.\n\nAs part of mapping it has to do resize of console according to frame\nbuffer info. if this resize fails and returns from vc_do_resize() and\ncontinues further. At this point console and new frame buffer are mapped\nand sets display vars. Despite failure still it continue to proceed\nupdating the screen at later stages where vc_data is related to previous\nframe buffer and frame buffer info and display vars are mapped to new\nframe buffer and eventully leading to out-of-bounds write in\nfast_imageblit(). This bheviour is excepted only when fg_console is\nequal to requested console which is a visible console and updates screen\nwith invalid struct references in fbcon_putcs()."
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nfbdev: Corrección de escritura fuera de límites de vmalloc en fast_imageblit\n\nEste problema se activa cuando un programa de espacio de usuario realiza un ioctl FBIOPUT_CON2FBMAP pasando el número de consola y el número de búfer de fotogramas. Idealmente, esto mapea la consola al búfer de fotogramas y actualiza la pantalla si la consola está visible.\n\nComo parte del mapeo, tiene que realizar un redimensionamiento de la consola según la información del búfer de fotogramas. Si este redimensionamiento falla y regresa de vc_do_resize() y continúa más allá. En este punto, la consola y el nuevo búfer de fotogramas están mapeados y establece las variables de visualización. A pesar del fallo, aún así continúa procediendo a actualizar la pantalla en etapas posteriores donde vc_data está relacionado con el búfer de fotogramas anterior y la información del búfer de fotogramas y las variables de visualización están mapeadas al nuevo búfer de fotogramas y eventualmente llevando a una escritura fuera de límites en fast_imageblit(). Este comportamiento se espera solo cuando fg_console es igual a la consola solicitada, que es una consola visible, y actualiza la pantalla con referencias de estructura inválidas en fbcon_putcs()."
    }
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