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CVE-2025-40323

Estado: AplazadaAlta (7.8)—

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

fbcon: Set fb_display[i]->mode to NULL when the mode is released

Recently, we discovered the following issue through syzkaller:

Based on experimentation and analysis, during framebuffer unregistration, only the memory of fb_info->modelist is freed, without setting the corresponding fb_display[i]->mode to NULL for the freed modes. This leads to UAF issues during subsequent accesses. Here's an example of reproduction steps: 1.

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With /dev/fb0 already registered in the system, load a kernel module to register a new device /dev/fb1; 2. Set fb1's mode to the global fb_display[] array (via FBIOPUT_CON2FBMAP); 3. Switch console from fb to VGA (to allow normal rmmod of the ko); 4. Unload the kernel module, at this point fb1's modelist is freed, leaving a wild pointer in fb_display[]; 5. Trigger the bug via system calls through fb0 attempting to delete a mode from fb0.

Add a check in do_unregister_framebuffer(): if the mode to be freed exists in fb_display[], set the corresponding mode pointer to NULL.

Detalles técnicos trazas, registros y código del informe original
BUG: KASAN: slab-use-after-free in fb_mode_is_equal+0x285/0x2f0
Read of size 4 at addr ff11000001b3c69c by task syz.xxx
...
Call Trace:
 <TASK>
 dump_stack_lvl+0xab/0xe0
 print_address_description.constprop.0+0x2c/0x390
 print_report+0xb9/0x280
 kasan_report+0xb8/0xf0
 fb_mode_is_equal+0x285/0x2f0
 fbcon_mode_deleted+0x129/0x180
 fb_set_var+0xe7f/0x11d0
 do_fb_ioctl+0x6a0/0x750
 fb_ioctl+0xe0/0x140
 __x64_sys_ioctl+0x193/0x210
 do_syscall_64+0x5f/0x9c0
 entry_SYSCALL_64_after_hwframe+0x76/0x7e

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:L/PR:L sin UI indica escalada local. Use-after-free en fbcon permite DoS (crash kernel) e info disclosure via acceso a memoria liberada.

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 ProgramFilter Network TrafficExecution PreventionApplication Isolation and SandboxingExploit ProtectionUpdate Software

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-2025-40323",
  "cveTags": [],
  "metrics": {
    "cvssMetricV31": [
      {
        "type": "Secondary",
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "cvssData": {
          "scope": "UNCHANGED",
          "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",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "confidentialityImpact": "HIGH"
        },
        "impactScore": 5.9,
        "exploitabilityScore": 1.8
      }
    ]
  },
  "affected": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "affectedData": [
        {
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "product": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
              "lessThan": "39c2c1a2773aaf73e56906e5ef670114eb2d354f",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
              "lessThan": "4ac18f0e6a6d599ca751c4cd98e522afc8e3d4eb",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
              "lessThan": "468f78276a37f4c6499385a4ce28f4f57be6655d",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
              "lessThan": "c079d42f70109512eee49123a843be91d8fa133f",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
              "lessThan": "de89d19f4f30d9a8de87b9d08c1bd35cb70576d8",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
              "lessThan": "a1f3058930745d2b938b6b4f5bd9630dc74b26b7",
              "versionType": "git"
            }
          ],
          "programFiles": [
            "drivers/video/fbdev/core/fbcon.c",
            "drivers/video/fbdev/core/fbmem.c",
            "include/linux/fbcon.h"
          ],
          "defaultStatus": "unaffected"
        },
        {
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "product": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "2.6.12"
            },
            {
              "status": "unaffected",
              "version": "0",
              "lessThan": "2.6.12",
              "versionType": "semver"
            },
            {
              "status": "unaffected",
              "version": "5.15.203",
              "versionType": "semver",
              "lessThanOrEqual": "5.15.*"
            },
            {
              "status": "unaffected",
              "version": "6.1.159",
              "versionType": "semver",
              "lessThanOrEqual": "6.1.*"
            },
            {
              "status": "unaffected",
              "version": "6.6.117",
              "versionType": "semver",
              "lessThanOrEqual": "6.6.*"
            },
            {
              "status": "unaffected",
              "version": "6.12.58",
              "versionType": "semver",
              "lessThanOrEqual": "6.12.*"
            },
            {
              "status": "unaffected",
              "version": "6.17.8",
              "versionType": "semver",
              "lessThanOrEqual": "6.17.*"
            },
            {
              "status": "unaffected",
              "version": "6.18",
              "versionType": "original_commit_for_fix",
              "lessThanOrEqual": "*"
            }
          ],
          "programFiles": [
            "drivers/video/fbdev/core/fbcon.c",
            "drivers/video/fbdev/core/fbmem.c",
            "include/linux/fbcon.h"
          ],
          "defaultStatus": "affected"
        }
      ]
    }
  ],
  "published": "2025-12-08T01:16:05.067",
  "references": [
    {
      "url": "https://git.kernel.org/stable/c/39c2c1a2773aaf73e56906e5ef670114eb2d354f",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/468f78276a37f4c6499385a4ce28f4f57be6655d",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/4ac18f0e6a6d599ca751c4cd98e522afc8e3d4eb",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/a1f3058930745d2b938b6b4f5bd9630dc74b26b7",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/c079d42f70109512eee49123a843be91d8fa133f",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/de89d19f4f30d9a8de87b9d08c1bd35cb70576d8",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "vulnStatus": "Deferred",
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nfbcon: Set fb_display[i]->mode to NULL when the mode is released\n\nRecently, we discovered the following issue through syzkaller:\n\nBUG: KASAN: slab-use-after-free in fb_mode_is_equal+0x285/0x2f0\nRead of size 4 at addr ff11000001b3c69c by task syz.xxx\n...\nCall Trace:\n <TASK>\n dump_stack_lvl+0xab/0xe0\n print_address_description.constprop.0+0x2c/0x390\n print_report+0xb9/0x280\n kasan_report+0xb8/0xf0\n fb_mode_is_equal+0x285/0x2f0\n fbcon_mode_deleted+0x129/0x180\n fb_set_var+0xe7f/0x11d0\n do_fb_ioctl+0x6a0/0x750\n fb_ioctl+0xe0/0x140\n __x64_sys_ioctl+0x193/0x210\n do_syscall_64+0x5f/0x9c0\n entry_SYSCALL_64_after_hwframe+0x76/0x7e\n\nBased on experimentation and analysis, during framebuffer unregistration,\nonly the memory of fb_info->modelist is freed, without setting the\ncorresponding fb_display[i]->mode to NULL for the freed modes. This leads\nto UAF issues during subsequent accesses. Here's an example of reproduction\nsteps:\n1. With /dev/fb0 already registered in the system, load a kernel module\n   to register a new device /dev/fb1;\n2. Set fb1's mode to the global fb_display[] array (via FBIOPUT_CON2FBMAP);\n3. Switch console from fb to VGA (to allow normal rmmod of the ko);\n4. Unload the kernel module, at this point fb1's modelist is freed, leaving\n   a wild pointer in fb_display[];\n5. Trigger the bug via system calls through fb0 attempting to delete a mode\n   from fb0.\n\nAdd a check in do_unregister_framebuffer(): if the mode to be freed exists\nin fb_display[], set the corresponding mode pointer to NULL."
    }
  ],
  "lastModified": "2026-07-30T06:24:29.200",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}