GHSA-MPPP-59PM-FQXW

Vulnerability from github – Published: 2026-07-19 12:30 – Updated: 2026-07-19 12:30
VLAI
Details

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

fbdev: Fix fb_new_modelist to prevent null-ptr-deref in fb_videomode_to_var

info->var, a framebuffer's current mode, is expected to have a matching entry in info->modelist. var_to_display() relies on this and treats a failed fb_match_mode() as "This should not happen". fb_set_var() keeps it true by adding the mode to the list on every change, and do_register_framebuffer() does the same at registration.

store_modes() replaces the modelist from userspace. fb_new_modelist() validates the new modes but does not check that info->var still has a match. It relies on fbcon_new_modelist() to re-point consoles, but that only handles consoles mapped to the framebuffer. With fbcon unbound there are none, so info->var is left describing a mode that is no longer in the list.

A later console takeover runs var_to_display(), where fb_match_mode() returns NULL and leaves fb_display[i].mode NULL. fbcon_switch() passes it to display_to_var(), and fb_videomode_to_var() dereferences the NULL mode.

Keep the current mode in the list in fb_new_modelist(), the same way fb_set_var() does.

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{
  "affected": [],
  "aliases": [
    "CVE-2026-53403"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-07-19T12:16:51Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nfbdev: Fix fb_new_modelist to prevent null-ptr-deref in fb_videomode_to_var\n\ninfo-\u003evar, a framebuffer\u0027s current mode, is expected to have a matching\nentry in info-\u003emodelist. var_to_display() relies on this and treats a\nfailed fb_match_mode() as \"This should not happen\". fb_set_var() keeps it\ntrue by adding the mode to the list on every change, and\ndo_register_framebuffer() does the same at registration.\n\nstore_modes() replaces the modelist from userspace. fb_new_modelist()\nvalidates the new modes but does not check that info-\u003evar still has a\nmatch. It relies on fbcon_new_modelist() to re-point consoles, but that\nonly handles consoles mapped to the framebuffer. With fbcon unbound there\nare none, so info-\u003evar is left describing a mode that is no longer in the\nlist.\n\nA later console takeover runs var_to_display(), where fb_match_mode()\nreturns NULL and leaves fb_display[i].mode NULL. fbcon_switch() passes it\nto display_to_var(), and fb_videomode_to_var() dereferences the NULL mode.\n\nKeep the current mode in the list in fb_new_modelist(), the same way\nfb_set_var() does.",
  "id": "GHSA-mppp-59pm-fqxw",
  "modified": "2026-07-19T12:30:23Z",
  "published": "2026-07-19T12:30:23Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-53403"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/0d8c7f21ad8529d5c181e61f86be35b887ae2e4d"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/1458a4d804550b7101e8bb02c1cb941088e4c0c7"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/4f1a7fe8ba845cb7d39580755f78c3b7b9a0b61e"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/7640b4f68acb54c2c4f6b4a8aee0e9849dacd929"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/7f08fc10fa3d3366dc3af723970bd03d7d6d10e3"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/8707f02ac9f5f632039b60df2c9f3dc914709f72"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/88913059c77e171f44ba829282d42dde0d458811"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/eea16b6f805c0b1fb2f72f0f771088ea45356956"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}



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