Bug 2516790 (CVE-2026-74424)

Summary: CVE-2026-74424 kernel: fbcon: fix NULL pointer dereference for a console without vc_data
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel. The `fbcon` component, responsible for framebuffer console operations, can encounter a NULL pointer dereference. This occurs when `fbcon_new_modelist()` attempts to access console data (`vc_data`) that has been freed, leading to a system crash. A local attacker could potentially trigger this issue, resulting in a Denial of Service (DoS).
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Description OSIDB Bzimport 2026-08-15 06:33:37 UTC 
In the Linux kernel, the following vulnerability has been resolved:

fbcon: fix NULL pointer dereference for a console without vc_data

fbcon_new_modelist() runs when a framebuffer's modelist changes. For each
console mapped to it with fb_display[i].mode set, it reads vc_cons[i].d and
passes the vc_num to fbcon_set_disp(). This assumes a console with a mode
set has a vc_data, but it can be NULL. fbcon_set_disp() sets
fb_display[i].mode before it checks vc_data, and fbcon_deinit() leaves the
mode set after the vc_data is freed. fbcon_new_modelist() then dereferences
the NULL vc_data.

Keep fb_display[i].mode set only while the console has a vc_data. Check
vc_data before setting the mode in fbcon_set_disp(), and clear the mode in
fbcon_deinit(). The existing mode check in fbcon_new_modelist() then skips
such consoles.
Comment 1 Keith Grant 2026-08-20 22:13:35 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026081513-CVE-2026-74424-2cab@gregkh/T