CVE-2026-53402: 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 fbco...

Description

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.

Metrics

CVSS 3.1

7.1/10

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H

EPSS Probability

0.13%

2.9th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

Vendor	Product	Versions
Linux	Linux	>= 868749a7456dc48e93887a8474194e2ee6d6c21f, < cb016bcb40c81e7b19c4ae6143babb366dae8e20; >= ebd6f886aa2447fcfcdce5450c9e1028e1d681bb, < ac562193c36696513ae196171892e9338475c4bc; >= a5a923038d70d2d4a86cb4e3f32625a5ee6e7e24, < 3618a4c5b2591cfa83efe74f5b18c2d02b35c3f5; >= a5a923038d70d2d4a86cb4e3f32625a5ee6e7e24, < a7a526fbc847f07ad3a503c7382189be5ab68574; >= a5a923038d70d2d4a86cb4e3f32625a5ee6e7e24, < b5bb2c696e140c399cb874def2feedf61dee27d6; >= a5a923038d70d2d4a86cb4e3f32625a5ee6e7e24, < 076b1aa65f77a49bce5a48a4a55a397cfcafa2b8; >= a5a923038d70d2d4a86cb4e3f32625a5ee6e7e24, < 39815715cbcfabb16fc8c5f4a23deeda20f5df62; >= a5a923038d70d2d4a86cb4e3f32625a5ee6e7e24, < 8fdc8c2057eea08d40ce2c8eed41ff9e451c65c2; f08ccb792d3eaf1dc62d8cbf6a30d6522329f660; >= 5.10.249, < 5.10.261; >= 5.15.64, < 5.15.212; >= 5.19.6, < 5.20
Linux	Linux	6.0

References

Timeline

Published: Jul 19, 2026
Last Modified: Jul 27, 2026
Status: Awaiting Analysis

Frequently Asked Questions

What is CVE-2026-53402?

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.

How severe is CVE-2026-53402?

CVE-2026-53402 has a CVSS score of 7.1/10 (HIGH severity). The EPSS model estimates a 0.13% probability of exploitation in the next 30 days.

How do I fix CVE-2026-53402?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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