CVE-2025-40322 fbdev: bitblit: bound-check glyph index in bit_putcs*
An out-of-bounds read in the Linux kernel framebuffer driver allows attackers to read memory beyond the font array boundaries.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-40322?
CVE-2025-40322 is a high-severity vulnerability in Linux, published on 8 Dec 2025. 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:
fbdev: bitblit: bound-check glyph index in bit_putcs*
bit_putcs_aligned()/unaligned() derived the glyph pointer from the character value masked by 0xff/0x1ff, which may exceed the actual font's glyph count and read past the end of the built-in font array. Clamp the index to the actual glyph count before computing the address.
This fixes a global out-of-bounds read reported by syzbot.
Which versions are affected by CVE-2025-40322?
How do I fix CVE-2025-40322?
Apply the vendor's patch.
Is CVE-2025-40322 being exploited?
There is no known exploitation of CVE-2025-40322 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2025-40322, DEBIAN-CVE-2025-40322, GHSA-hcc6-6437-vwm2, ROOT-OS-DEBIAN-12-CVE-2025-40322, ROOT-OS-DEBIAN-13-CVE-2025-40322, ROOT-OS-UBUNTU-2204-CVE-2025-40322 and 2 more.