CVE-2025-68725 bpf: Do not let BPF test infra emit invalid GSO types to stack
A flaw in the Linux kernel BPF test infrastructure allows triggering invalid GSO types, potentially causing warnings or denial of service.
- 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-2025-68725?
CVE-2025-68725 is a medium-severity vulnerability in Linux kernel, published on 24 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:
bpf: Do not let BPF test infra emit invalid GSO types to stack
Yinhao et al. reported that their fuzzer tool was able to trigger a skb_warn_bad_offload() from netif_skb_features() -> gso_features_check(). When a BPF program - triggered via BPF test infra - pushes the packet to the loopback device via bpf_clone_redirect() then mentioned offload warning can be seen. GSO-related features are then rightfully disabled.
We get into this situation due to convert___skb_to_skb() setting gso_segs and gso_size but not gso_type. Technically, it makes sense that this warning triggers since the GSO properties are malformed due to the gso_type. Potentially, the gso_type could be marked non-trustworthy through setting it at least to SKB_GSO_DODGY without any other specific assumptions, but that also feels wrong given we should not go further into the GSO engine in the first place.
The checks were added in 121d57af308d ("gso: validate gso_type in GSO handlers") because there were malicious (syzbot) senders that combine a protocol with a non-matching gso_type. If we would want to drop such packets, gso_features_check() currently only returns feature flags via netif_skb_features(), so one location for potentially dropping such skbs could be validate_xmit_unreadable_skb(), but then otoh it would be an additional check in the fast-path for a very corner case. Given bpf_clone_redirect() is the only place where BPF test infra could emit such packets, lets reject them right there.
Which versions are affected by CVE-2025-68725?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2025-68725?
Apply the vendor's patch.
Is CVE-2025-68725 being exploited?
There is no known exploitation of CVE-2025-68725 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-73117, AZL-78413, BELL-CVE-2025-68725, DEBIAN-CVE-2025-68725, GHSA-696c-x544-xmc9, ROOT-OS-UBUNTU-2204-CVE-2025-68725 and 2 more.