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CVE-2021-47383

Disclosure Date: May 21, 2024 •
CVE-2021-47383
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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 Severity and Metrics
Base Score:
None
Impact Score:
Unknown
Exploitability Score:
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Vector:
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Attack Vector (AV):
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Attack Complexity (AC):
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Privileges Required (PR):
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User Interaction (UI):
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Scope (S):
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Confidentiality (C):
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Integrity (I):
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Availability (A):
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General Information

Offensive Application
Unknown
Utility Class
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Ports
Unknown
OS
Unknown
Vulnerable Versions
Linux 7e71fcedfda6
Linux not down converted
Prerequisites
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Discovered By
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PoC Author
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Metasploit Module
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Reporter
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Vendors

  • Linux

Products

  • Linux
Technical Analysis