Linux Kernel fbcon OOB Read in err_out Path due to Missing HiFont Rollback
CVE-2026-53402 Published on July 19, 2026
fbdev: fbcon: fix out-of-bounds read in err_out of fbcon_do_set_font()
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.
Products Associated with CVE-2026-53402
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Affected Versions
Linux:- Version 868749a7456dc48e93887a8474194e2ee6d6c21f and below cb016bcb40c81e7b19c4ae6143babb366dae8e20 is affected.
- Version ebd6f886aa2447fcfcdce5450c9e1028e1d681bb and below ac562193c36696513ae196171892e9338475c4bc is affected.
- Version a5a923038d70d2d4a86cb4e3f32625a5ee6e7e24 and below 3618a4c5b2591cfa83efe74f5b18c2d02b35c3f5 is affected.
- Version a5a923038d70d2d4a86cb4e3f32625a5ee6e7e24 and below a7a526fbc847f07ad3a503c7382189be5ab68574 is affected.
- Version a5a923038d70d2d4a86cb4e3f32625a5ee6e7e24 and below b5bb2c696e140c399cb874def2feedf61dee27d6 is affected.
- Version a5a923038d70d2d4a86cb4e3f32625a5ee6e7e24 and below 076b1aa65f77a49bce5a48a4a55a397cfcafa2b8 is affected.
- Version a5a923038d70d2d4a86cb4e3f32625a5ee6e7e24 and below 39815715cbcfabb16fc8c5f4a23deeda20f5df62 is affected.
- Version a5a923038d70d2d4a86cb4e3f32625a5ee6e7e24 and below 8fdc8c2057eea08d40ce2c8eed41ff9e451c65c2 is affected.
- Version f08ccb792d3eaf1dc62d8cbf6a30d6522329f660 is affected.
- Version 5.10.249 and below 5.10.261 is affected.
- Version 5.15.64 and below 5.15.212 is affected.
- Version 5.19.6 and below 5.20 is affected.
- Version 6.0 is affected.
- Before 6.0 is unaffected.
- Version 5.10.261, <= 5.10.* is unaffected.
- Version 5.15.212, <= 5.15.* is unaffected.
- Version 6.1.178, <= 6.1.* is unaffected.
- Version 6.6.145, <= 6.6.* is unaffected.
- Version 6.12.96, <= 6.12.* is unaffected.
- Version 6.18.39, <= 6.18.* is unaffected.
- Version 7.1.3, <= 7.1.* is unaffected.
- Version 7.2, <= * is unaffected.
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.