CVE-2025-40278 net: sched: act_ife: initialize struct tc_ife to fix KMSAN kernel-infoleak

Not scored Published 6 Dec 2025 Updated 2 Jun 2026

A local attacker can read uninitialized kernel memory via netlink messages due to improper initialization in the IFE action module.

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-2025-40278?

CVE-2025-40278 is a vulnerability in Linux, published on 6 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:

net: sched: act_ife: initialize struct tc_ife to fix KMSAN kernel-infoleak

Fix a KMSAN kernel-infoleak detected by the syzbot .

[net?] KMSAN: kernel-infoleak in __skb_datagram_iter

In tcf_ife_dump(), the variable 'opt' was partially initialized using a designatied initializer. While the padding bytes are reamined uninitialized. nla_put() copies the entire structure into a netlink message, these uninitialized bytes leaked to userspace.

Initialize the structure with memset before assigning its fields to ensure all members and padding are cleared prior to beign copied.

This change silences the KMSAN report and prevents potential information leaks from the kernel memory.

This fix has been tested and validated by syzbot. This patch closes the bug reported at the following syzkaller link and ensures no infoleak.

Which versions are affected by CVE-2025-40278?

How do I fix CVE-2025-40278?

Apply the vendor's patch.

Is CVE-2025-40278 being exploited?

There is no known exploitation of CVE-2025-40278 in the wild and no public exploit code.

Sources

Also known as BELL-CVE-2025-40278, DEBIAN-CVE-2025-40278, GHSA-8p8p-qx6g-jxw6, ROOT-OS-UBUNTU-2204-CVE-2025-40278, ROOT-OS-UBUNTU-2404-CVE-2025-40278, UBUNTU-CVE-2025-40278.