CVE-2021-47383: Linux Kernel

High severity, CVSS 7.1. EPSS: 0.3% chance of exploitation in the next 30 days.

In the Linux kernel, the following vulnerability has been resolved: tty: Fix out-of-bound vmalloc access in imageblit This issue happens when a userspace program does an ioctl FBIOPUT_VSCREENINFO passing the fb_var_screeninfo struct containing only the fields xres, yres, and bits_per_pixel with values. If this struct is the same as the previous ioctl, the vc_resize() detects it and doesn't call the resize_screen(), leaving the fb_var_screeninfo incomplete. And this leads to the updatescrollmode() calculates a wrong value to fbcon_display->vrows, which makes the real_y() return a wrong value of y, and that value, eventually, causes the imageblit to access an out-of-bound address value. To solve this issue I made the resize_screen() be called even if the screen does not need any resizing, so it will "fix and fill" the fb_var_screeninfo independently.

Affected products

• Linux Linux Kernel: before 4.4.286 (fixed in 4.4.286); from 4.5, before 4.9.285 (fixed in 4.9.285); from 4.10, before 4.14.249 (fixed in 4.14.249); from 4.15, before 4.19.209 (fixed in 4.19.209); from 4.20, before 5.4.151 (fixed in 5.4.151); from 5.5, before 5.10.71 (fixed in 5.10.71); …

Published 2024-05-21. Last modified 2026-08-04.