Linux Kernel up to 6.12.95/6.18.38/7.1.2/7.2 Fbcon drivers/video/fbcon.c fbcon_do_set_font vc_hi_font_mask out-of-bounds

Summaryinfo

A vulnerability was found in Linux Kernel up to 6.12.95/6.18.38/7.1.2/7.2. It has been classified as critical. The affected element is the function fbcon_do_set_font of the file drivers/video/fbcon.c of the component Fbcon. Performing a manipulation of the argument vc_hi_font_mask results in out-of-bounds. This vulnerability was named CVE-2026-53402. The attack may be initiated remotely. There is no available exploit.

Detailsinfo

A vulnerability classified as critical has been found in Linux Kernel up to 6.12.95/6.18.38/7.1.2/7.2. This affects the function fbcon_do_set_font of the file drivers/video/fbcon.c of the component Fbcon. The manipulation of the argument vc_hi_font_mask with an unknown input leads to a out-of-bounds vulnerability. CWE is classifying the issue as CWE-125. The product reads data past the end, or before the beginning, of the intended buffer. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: fbdev: fbcon: fix out-of-bounds read in err_out of fbcon_do_set_font() When fbcon_do_set_font() fails (e.g., due to a memory allocation failure inside vc_resize() under heavy memory pressure), it jumps to the `err_out` label to roll back the console state. However, the current rollback logic forgets to restore the `hi_font` state, leading to a severe state machine corruption. Earlier in the function, `set_vc_hi_font()` might be called to change `vc->vc_hi_font_mask` and mutate the screen buffer. If `vc_resize()` subsequently fails, the `err_out` path restores `vc_font.charcount` but entirely skips rolling back the `vc_hi_font_mask` and the screen buffer. This mismatch leaves the terminal in a desynchronized state. Because `vc_hi_font_mask` remains set, the VT subsystem will still accept character indices greater than 255 from userspace and write them to the screen buffer. Subsequent rendering calls (e.g., `fbcon_putcs()`) will then use these inflated indices to access the reverted, 256-character font array, leading to a deterministic out-of-bounds read and potential kernel memory disclosure. Fix this by adding the missing rollback logic for the `hi_font` mask and screen buffer in the error path.

The advisory is shared at git.kernel.org. This vulnerability is uniquely identified as CVE-2026-53402 since 06/09/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. It demands that the victim is doing some kind of user interaction. Technical details are known, but no exploit is available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 07/19/2026).

Upgrading to version 6.12.96, 6.18.39, 7.1.3 or 7.2-rc1 eliminates this vulnerability.

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Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.12.0
• 6.12.1
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• 6.12.95
• 6.18.0
• 6.18.1
• 6.18.2
• 6.18.3
• 6.18.4
• 6.18.5
• 6.18.6
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• 6.18.38
• 7.0
• 7.1
• 7.1.0
• 7.1.1
• 7.1.2
• 7.2

License

• open-source

Website

• Vendor: https://www.kernel.org/

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Entryinfo

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