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CVE-2026-53403

Status: AnalyzedMedium (5.5)—

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.

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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.

CVSS

Exploitation probability (EPSS)

EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).

Affected technologies (1)

CWEs

References

Raw JSON (NVD)

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      "value": "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->var, a framebuffer's current mode, is expected to have a matching\nentry in info->modelist. 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->var 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->var 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."
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