CVE-2025-40350 net/mlx5e: RX, Fix generating skb from non-linear xdp_buff for striding RQ
A bug in the mlx5 network driver causes kernel warnings or crashes when XDP programs modify buffer layouts, leading to denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-40350?
CVE-2025-40350 is a critical vulnerability in Linux, published on 16 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:
net/mlx5e: RX, Fix generating skb from non-linear xdp_buff for striding RQ
XDP programs can change the layout of an xdp_buff through bpf_xdp_adjust_tail() and bpf_xdp_adjust_head(). Therefore, the driver cannot assume the size of the linear data area nor fragments. Fix the bug in mlx5 by generating skb according to xdp_buff after XDP programs run.
Currently, when handling multi-buf XDP, the mlx5 driver assumes the layout of an xdp_buff to be unchanged. That is, the linear data area continues to be empty and fragments remain the same. This may cause the driver to generate erroneous skb or triggering a kernel warning. When an XDP program added linear data through bpf_xdp_adjust_head(), the linear data will be ignored as mlx5e_build_linear_skb() builds an skb without linear data and then pull data from fragments to fill the linear data area. When an XDP program has shrunk the non-linear data through bpf_xdp_adjust_tail(), the delta passed to __pskb_pull_tail() may exceed the actual nonlinear data size and trigger the BUG_ON in it.
To fix the issue, first record the original number of fragments. If the number of fragments changes after the XDP program runs, rewind the end fragment pointer by the difference and recalculate the truesize. Then, build the skb with the linear data area matching the xdp_buff. Finally, only pull data in if there is non-linear data and fill the linear part up to 256 bytes.
Which versions are affected by CVE-2025-40350?
How do I fix CVE-2025-40350?
Apply the vendor's patch.
Is CVE-2025-40350 being exploited?
There is no known exploitation of CVE-2025-40350 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2025-40350, DEBIAN-CVE-2025-40350, GHSA-xffx-64g2-mrvp, ROOT-OS-UBUNTU-2404-CVE-2025-40350, UBUNTU-CVE-2025-40350.