Attacker Value
Unknown
(0 users assessed)
Exploitability
Unknown
(0 users assessed)
User Interaction
None
Privileges Required
Low
Attack Vector
Local
0

CVE-2024-50048

Disclosure Date: October 21, 2024 •
CVE-2024-50048 CVSS v3 Base Score: 5.5
Add MITRE ATT&CK tactics and techniques that apply to this CVE.

Description

In the Linux kernel, the following vulnerability has been resolved:

fbcon: Fix a NULL pointer dereference issue in fbcon_putcs

syzbot has found a NULL pointer dereference bug in fbcon.
Here is the simplified C reproducer:

struct param {

uint8_t type;
struct tiocl_selection ts;

};

int main()
{

struct fb_con2fbmap con2fb;
struct param param;

int fd = open("/dev/fb1", 0, 0);

con2fb.console = 0x19;
con2fb.framebuffer = 0;
ioctl(fd, FBIOPUT_CON2FBMAP, &con2fb);

param.type = 2;
param.ts.xs = 0; param.ts.ys = 0;
param.ts.xe = 0; param.ts.ye = 0;
param.ts.sel_mode = 0;

int fd1 = open("/dev/tty1", O_RDWR, 0);
ioctl(fd1, TIOCLINUX, &param);

con2fb.console = 1;
con2fb.framebuffer = 0;
ioctl(fd, FBIOPUT_CON2FBMAP, &con2fb);

return 0;

}

After calling ioctl(fd1, TIOCLINUX, &param), the subsequent ioctl(fd, FBIOPUT_CON2FBMAP, &con2fb)
causes the kernel to follow a different execution path:

set_con2fb_map
–> con2fb_init_display
–> fbcon_set_disp

-> redraw_screen
 -> hide_cursor
  -> clear_selection
   -> highlight
    -> invert_screen
     -> do_update_region
      -> fbcon_putcs
       -> ops->putcs

Since ops->putcs is a NULL pointer, this leads to a kernel panic.
To prevent this, we need to call set_blitting_type() within set_con2fb_map()
to properly initialize ops->putcs.

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CVSS V3 Severity and Metrics
Base Score:
5.5 Medium
Impact Score:
3.6
Exploitability Score:
1.8
Vector:
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Attack Vector (AV):
Local
Attack Complexity (AC):
Low
Privileges Required (PR):
Low
User Interaction (UI):
None
Scope (S):
Unchanged
Confidentiality (C):
None
Integrity (I):
None
Availability (A):
High

General Information

Offensive Application
Unknown
Utility Class
Unknown
Ports
Unknown
OS
Unknown
Vulnerable Versions
Linux 8266ae6eafdc
Linux not down converted
Prerequisites
Unknown
Discovered By
Unknown
PoC Author
Unknown
Metasploit Module
Unknown
Reporter
Unknown

Vendors

  • linux

Products

  • linux kernel
Technical Analysis