CVE-2026-63826 (GCVE-0-2026-63826)
Vulnerability from cvelistv5
Published
2026-07-19 12:02
Modified
2026-08-17 04:51
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: fbdev: fix use-after-free in store_modes() store_modes() replaces a framebuffer's modelist with modes from userspace. On success it frees the old modelist with fb_destroy_modelist(). Two fields still point into that freed list. One pointer is fb_display[i].mode, the mode a console is using. fbcon_new_modelist() moves these pointers to the new list. It only does so for consoles still mapped to the framebuffer. An unmapped console is skipped and keeps its stale pointer. Unbinding fbcon, for example, sets con2fb_map[i] to -1 but leaves fb_display[i].mode set. An FBIOPUT_VSCREENINFO ioctl with FB_ACTIVATE_INV_MODE later reaches fbcon_mode_deleted(). That function reads the stale fb_display[i].mode through fb_mode_is_equal(). The read is a use-after-free. The other pointer is fb_info->mode, the current mode. It is set through the mode sysfs attribute. store_modes() does not update fb_info->mode, so it is left pointing into the freed list. show_mode(), the attribute's read handler, dereferences the stale fb_info->mode through mode_string(). The read is a use-after-free. Clear both pointers before freeing the list. Commit a1f305893074 ("fbcon: Set fb_display[i]->mode to NULL when the mode is released") added the helper fbcon_delete_modelist(). It clears every fb_display[i].mode that points into a given list. So far it is called only from the unregister path. Call it from store_modes() too, and set fb_info->mode to NULL.
References
Impacted products
Vendor Product Version
Linux Linux Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
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{
  "containers": {
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        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/video/fbdev/core/fbsysfs.c"
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          ],
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          "vendor": "Linux",
          "versions": [
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              "status": "unaffected",
              "version": "7.1.3",
              "versionType": "semver"
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            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix"
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      ],
      "cpeApplicability": [
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          "nodes": [
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nfbdev: fix use-after-free in store_modes()\n\nstore_modes() replaces a framebuffer\u0027s modelist with modes from userspace.\nOn success it frees the old modelist with fb_destroy_modelist(). Two\nfields still point into that freed list.\n\nOne pointer is fb_display[i].mode, the mode a console is using.\nfbcon_new_modelist() moves these pointers to the new list. It only does so\nfor consoles still mapped to the framebuffer. An unmapped console is\nskipped and keeps its stale pointer. Unbinding fbcon, for example, sets\ncon2fb_map[i] to -1 but leaves fb_display[i].mode set. An\nFBIOPUT_VSCREENINFO ioctl with FB_ACTIVATE_INV_MODE later reaches\nfbcon_mode_deleted(). That function reads the stale fb_display[i].mode\nthrough fb_mode_is_equal(). The read is a use-after-free.\n\nThe other pointer is fb_info-\u003emode, the current mode. It is set through\nthe mode sysfs attribute. store_modes() does not update fb_info-\u003emode, so\nit is left pointing into the freed list. show_mode(), the attribute\u0027s read\nhandler, dereferences the stale fb_info-\u003emode through mode_string(). The\nread is a use-after-free.\n\nClear both pointers before freeing the list. Commit a1f305893074 (\"fbcon:\nSet fb_display[i]-\u003emode to NULL when the mode is released\") added the\nhelper fbcon_delete_modelist(). It clears every fb_display[i].mode that\npoints into a given list. So far it is called only from the unregister\npath. Call it from store_modes() too, and set fb_info-\u003emode to NULL."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-17T04:51:34.684Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/5267eab88fa4c684459504b8be577ad64953b9a6"
        },
        {
          "url": "https://git.kernel.org/stable/c/c6765f39ed27014ff877b00a2efa494233404e17"
        },
        {
          "url": "https://git.kernel.org/stable/c/0d35f9f194a858567a21017d69318a51e3a822b9"
        },
        {
          "url": "https://git.kernel.org/stable/c/70f1e000b88cfa8ca3fd7f4d082647fc089a7769"
        },
        {
          "url": "https://git.kernel.org/stable/c/2c1c805c65fb7dc7524e20376d6987721e73a0b1"
        }
      ],
      "title": "fbdev: fix use-after-free in store_modes()",
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      }
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  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-63826",
    "datePublished": "2026-07-19T12:02:21.518Z",
    "dateReserved": "2026-07-19T07:54:57.014Z",
    "dateUpdated": "2026-08-17T04:51:34.684Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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