CVE-2024-50048 fbcon: Fix a NULL pointer dereference issue in fbcon_putcs

What is CVE-2024-50048?

CVE-2024-50048 is a medium-severity vulnerability in Linux kernel, published on 21 Oct 2024. It can only be exploited from the same machine or local network, with no action from the victim.

Official 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.

Weakness: CWE-476

Which versions are affected by CVE-2024-50048?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2024-50048?

Apply the vendor's patch.

Is CVE-2024-50048 being exploited?

There is no known exploitation of CVE-2024-50048 in the wild and no public exploit code.

Other vulnerabilities in Linux kernel

• CVE-2026-53266 Linux Kernel Out-of-Bounds Write Exploited High 8.8
• CVE-2013-6282 Linux Kernel Improper Input Validation Exploited High 8.8
• CVE-2022-0185 Linux Kernel Heap-Based Buffer Overflow Exploited High 8.4
• CVE-2013-2094 Linux Kernel Privilege Escalation Exploited High 8.4
• CVE-2026-53362 Linux Kernel Unspecified Exploited High 7.8

All Linux kernel vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as AZL-50791, AZL-50942, BELL-CVE-2024-50048, DEBIAN-CVE-2024-50048, GHSA-fxqx-qp67-xrvv, ROOT-OS-UBUNTU-2204-CVE-2024-50048 and 1 more.