CVE-2025-68363 bpf: Check skb->transport_header is set in bpf_skb_check_mtu
A missing check in the Linux kernel BPF helper allows local attackers to trigger a kernel warning or potential crash via crafted network packets.
- 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-2025-68363?
CVE-2025-68363 is a vulnerability in Linux, 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: Check skb->transport_header is set in bpf_skb_check_mtu
The bpf_skb_check_mtu helper needs to use skb->transport_header when the BPF_MTU_CHK_SEGS flag is used:
bpf_skb_check_mtu(skb, ifindex, &mtu_len, 0, BPF_MTU_CHK_SEGS)
The transport_header is not always set. There is a WARN_ON_ONCE report when CONFIG_DEBUG_NET is enabled + skb->gso_size is set + bpf_prog_test_run is used:
WARNING: CPU: 1 PID: 2216 at ./include/linux/skbuff.h:3071 skb_gso_validate_network_len bpf_skb_check_mtu bpf_prog_3920e25740a41171_tc_chk_segs_flag # A test in the next patch bpf_test_run bpf_prog_test_run_skb
For a normal ingress skb (not test_run), skb_reset_transport_header is performed but there is plan to avoid setting it as described in commit 2170a1f09148 ("net: no longer reset transport_header in __netif_receive_skb_core()").
This patch fixes the bpf helper by checking skb_transport_header_was_set(). The check is done just before skb->transport_header is used, to avoid breaking the existing bpf prog. The WARN_ON_ONCE is limited to bpf_prog_test_run, so targeting bpf-next.
Which versions are affected by CVE-2025-68363?
How do I fix CVE-2025-68363?
Apply the vendor's patch.
Is CVE-2025-68363 being exploited?
There is no known exploitation of CVE-2025-68363 in the wild and no public exploit code.
Sources
Also known as AZL-73135, BELL-CVE-2025-68363, DEBIAN-CVE-2025-68363, GHSA-xphm-v24c-73f6, ROOT-OS-DEBIAN-12-CVE-2025-68363, ROOT-OS-UBUNTU-2204-CVE-2025-68363 and 2 more.