CVE-2025-39967 fbcon: fix integer overflow in fbcon_do_set_font
An integer overflow in the Linux kernel's fbcon font handling allows attackers to trigger buffer overflows, potentially leading to code execution or privilege escalation.
- 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-2025-39967?
CVE-2025-39967 is a high-severity vulnerability in Linux kernel, published on 15 Oct 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:
fbcon: fix integer overflow in fbcon_do_set_font
Fix integer overflow vulnerabilities in fbcon_do_set_font() where font size calculations could overflow when handling user-controlled font parameters.
The vulnerabilities occur when: 1. CALC_FONTSZ(h, pitch, charcount) performs h * pith * charcount multiplication with user-controlled values that can overflow. 2. FONT_EXTRA_WORDS * sizeof(int) + size addition can also overflow 3. This results in smaller allocations than expected, leading to buffer overflows during font data copying.
Add explicit overflow checking using check_mul_overflow() and check_add_overflow() kernel helpers to safety validate all size calculations before allocation.
Weakness: CWE-190
Which versions are affected by CVE-2025-39967?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2025-39967?
Apply the vendor's patch.
Is CVE-2025-39967 being exploited?
There is no known exploitation of CVE-2025-39967 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-68468, AZL-76440, BELL-CVE-2025-39967, DEBIAN-CVE-2025-39967, GHSA-xjw8-49g8-mg8p, ROOT-OS-DEBIAN-11-CVE-2025-39967 and 4 more.