CVE-2021-47383

HIGH
Published May 21, 2024 Modified Dec 10, 2025 CWE-125

Description

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.

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CVSS v3.1 Score

7.1
HIGH
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H

Weakness Type (CWE)

CWE-125 Out-of-bounds Read

Affected Products

Vendor Product
linux linux_kernel
linux linux_kernel
linux linux_kernel
linux linux_kernel
linux linux_kernel
linux linux_kernel
linux linux_kernel

References

Advisories & Patches

https://git.kernel.org/stable/c/067c694d06040db6f0c65281bb358452ca6d85b9 https://git.kernel.org/stable/c/3b0c406124719b625b1aba431659f5cdc24a982c https://git.kernel.org/stable/c/699d926585daa6ec44be556cdc1ab89e5d54557b https://git.kernel.org/stable/c/70aed03b1d5a5df974f456cdc8eedb213c94bb8b https://git.kernel.org/stable/c/7e71fcedfda6f7de18f850a6b36e78d78b04476f https://git.kernel.org/stable/c/883f7897a25e3ce14a7f274ca4c73f49ac84002a https://git.kernel.org/stable/c/8a6a240f52e14356386030d8958ae8b1761d2325 https://git.kernel.org/stable/c/d570c48dd37dbe8fc6875d4461d01a9554ae2560 https://git.kernel.org/stable/c/067c694d06040db6f0c65281bb358452ca6d85b9 https://git.kernel.org/stable/c/3b0c406124719b625b1aba431659f5cdc24a982c https://git.kernel.org/stable/c/699d926585daa6ec44be556cdc1ab89e5d54557b https://git.kernel.org/stable/c/70aed03b1d5a5df974f456cdc8eedb213c94bb8b https://git.kernel.org/stable/c/7e71fcedfda6f7de18f850a6b36e78d78b04476f https://git.kernel.org/stable/c/883f7897a25e3ce14a7f274ca4c73f49ac84002a https://git.kernel.org/stable/c/8a6a240f52e14356386030d8958ae8b1761d2325 https://git.kernel.org/stable/c/d570c48dd37dbe8fc6875d4461d01a9554ae2560

Frequently Asked Questions

What is CVE-2021-47383? +
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. It has a CVSS v3.1 base score of 7.1 (HIGH).
How severe is CVE-2021-47383? +
CVE-2021-47383 has a CVSS v3.1 score of 7.1 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching.
What products are affected by CVE-2021-47383? +
CVE-2021-47383 affects products from linux, specifically: linux_kernel. Check the affected products table above for specific version ranges.
How do I check if I'm vulnerable to CVE-2021-47383? +
You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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