CVE-2025-40236 virtio-net: zero unused hash fields
An attacker can read uninitialized memory from virtio-net tunnel headers, potentially leaking sensitive kernel data.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-40236?
CVE-2025-40236 is a vulnerability in Linux, published on 4 Dec 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
virtio-net: zero unused hash fields
When GSO tunnel is negotiated virtio_net_hdr_tnl_from_skb() tries to initialize the tunnel metadata but forget to zero unused rxhash fields. This may leak information to another side. Fixing this by zeroing the unused hash fields.
Which versions are affected by CVE-2025-40236?
How do I fix CVE-2025-40236?
Apply the vendor's patch.
Is CVE-2025-40236 being exploited?
There is no known exploitation of CVE-2025-40236 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2025-40236, DEBIAN-CVE-2025-40236, GHSA-gp3c-chw3-pxcc, UBUNTU-CVE-2025-40236.