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CVE-2026-53402

fbdev: fbcon: fix out-of-bounds read in err_out of fbcon_do_set_font()

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 5.10.261, 5.15.212, 5.20, 6.1.178, 6.6.145, and 3 more
None on Exploit-DB, Metasploit or GitHub
  • Exploitation: none
  • Automatable: no
  • Technical impact: partial

Summary

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.

Timeline

  1. CVE published
  2. CISA SSVC assessment

    Exploitation: none · Automatable: no · Technical impact: partial

  3. Record last updated

Affected versions

  • Linux Linux

    From 868749a7456dc48e93887a8474194e2ee6d6c21f · fixed in cb016bcb40c81e7b19c4ae6143babb366dae8e20; From ebd6f886aa2447fcfcdce5450c9e1028e1d681bb · fixed in ac562193c36696513ae196171892e9338475c4bc; From a5a923038d70d2d4a86cb4e3f32625a5ee6e7e24 · fixed in 3618a4c5b2591cfa83efe74f5b18c2d02b35c3f5; From a5a923038d70d2d4a86cb4e3f32625a5ee6e7e24 · fixed in a7a526fbc847f07ad3a503c7382189be5ab68574; From a5a923038d70d2d4a86cb4e3f32625a5ee6e7e24 · fixed in b5bb2c696e140c399cb874def2feedf61dee27d6; From a5a923038d70d2d4a86cb4e3f32625a5ee6e7e24 · fixed in 076b1aa65f77a49bce5a48a4a55a397cfcafa2b8; From a5a923038d70d2d4a86cb4e3f32625a5ee6e7e24 · fixed in 39815715cbcfabb16fc8c5f4a23deeda20f5df62; From a5a923038d70d2d4a86cb4e3f32625a5ee6e7e24 · fixed in 8fdc8c2057eea08d40ce2c8eed41ff9e451c65c2; From 5.10.249 · fixed in 5.10.261; From 5.15.64 · fixed in 5.15.212; From 5.19.6 · fixed in 5.20

  • Linux Linux

    6.0

  • KernelLinux

    fixed in 5.10.261; From 5.11.0 · fixed in 5.15.212; From 5.16.0 · fixed in 6.1.178; From 6.0.0 · fixed in 6.6.145; From 6.2.0 · fixed in 6.12.96; From 6.7.0 · fixed in 6.18.39; From 6.13.0 · fixed in 7.1.3

References 8

git.kernel.org