CVE-2026-68337

Summary

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.

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/cabfacbd5af09d3ae898ca224c4a1459e9bba15d
• https://git.kernel.org/stable/c/3f4920d165b29052255527d8ae7619e7ec132ece

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