CVE-2025-40279 net: sched: act_connmark: initialize struct tc_ife to fix kernel leak
A local attacker can read uninitialized kernel memory via netlink messages due to improper structure initialization in the connmark action.
- 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-2025-40279?
CVE-2025-40279 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_connmark: initialize struct tc_ife to fix kernel leak
In tcf_connmark_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.
Which versions are affected by CVE-2025-40279?
How do I fix CVE-2025-40279?
Apply the vendor's patch.
Is CVE-2025-40279 being exploited?
There is no known exploitation of CVE-2025-40279 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2025-40279, DEBIAN-CVE-2025-40279, GHSA-85ch-f4p7-jj7h, ROOT-OS-DEBIAN-11-CVE-2025-40279, ROOT-OS-DEBIAN-12-CVE-2025-40279, ROOT-OS-DEBIAN-13-CVE-2025-40279 and 3 more.