CVE-2025-39967: Linux Kernel

High severity, CVSS 7.8. EPSS: 0.2% chance of exploitation in the next 30 days.

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.

Affected products

• Linux Linux Kernel: from 4.4.235, before 4.5 (fixed in 4.5); from 4.9.235, before 4.10 (fixed in 4.10); from 4.14.196, before 4.15 (fixed in 4.15); from 4.19.143, before 4.20 (fixed in 4.20); from 5.4.62, before 5.4.300 (fixed in 5.4.300); from 5.8.6, before 5.9 (fixed in 5.9); …

Published 2025-10-15. Last modified 2026-07-30.