CVE-2026-68337 bpf: Reject redirect helpers without a bpf_net_context
A local attacker with high privileges can cause a kernel crash by triggering a null pointer dereference in BPF redirect helpers when attached to specific qdiscs.
- Exploited in the wild
- Not known
- Login needed
- An administrator
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-68337?
CVE-2026-68337 is a vulnerability in Linux, published on 10 Aug 2026. 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: Reject redirect helpers without a bpf_net_context
The bpf_redirect*() helpers and skb_do_redirect() obtain the per-task bpf_redirect_info via bpf_net_ctx_get_ri(), which dereferences the current->bpf_net_context unconditionally. That context is established on the paths that run tc BPF such as sch_handle_{ingress,egress}(), *except* for the case where {cls,act}_bpf was attached to a proper qdisc. A program running from there reaches the NULL deref in two ways:
* It calls bpf_redirect() directly, which dereferences the context at the top of the helper:
tc qdisc add dev eth0 root handle 1: red limit 1MB min 10KB max 20KB \ avpkt 1000 burst 100 qevent early_drop block 10 tc filter add block 10 pref 1 bpf obj redirect.o
* It simply returns TC_ACT_REDIRECT without helper call: tcf_qevent_handle() then dispatches to skb_do_redirect(), which dereferences the context
Rather than extending bpf_net_context management into the qdisc path, make the redirect helpers refuse to operate when no context exists, and have tcf_qevent_handle() drop a TC_ACT_REDIRECT verdict instead of calling skb_do_redirect(). Previous behaviour was a crash, so nothing regresses by not supporting it.
Which versions are affected by CVE-2026-68337?
How do I fix CVE-2026-68337?
Apply the vendor's patch.
Is CVE-2026-68337 being exploited?
There is no known exploitation of CVE-2026-68337 in the wild and no public exploit code.
Sources
Also known as AZL-94701, BELL-CVE-2026-68337, DEBIAN-CVE-2026-68337, GHSA-r749-jhcj-5x93, UBUNTU-CVE-2026-68337.