net/sched: act_ct: preserve tc_skb_cb across defragmentation

Summary

In the Linux kernel, the following vulnerability has been resolved: net/sched: act_ct: preserve tc_skb_cb across defragmentation tcf_ct_handle_fragments() calls nf_ct_handle_fragments() without saving and restoring skb->cb. The defrag helper clears IPCB/IP6CB, which aliases the tc_skb_cb/qdisc_skb_cb control buffer. Fragmented traffic through act_ct therefore loses qdisc metadata such as pkt_segs and can trigger WARN_ON_ONCE() in qdisc_pkt_segs() when panic_on_warn is enabled. Save and restore the full tc_skb_cb around nf_ct_handle_fragments(), matching the pattern used by ovs_ct_handle_fragments().

Timeline

1. Aug 15, 2026, 5:52 AM UTCCVE published
2. Oct 16, 2026, 3:51 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: yes · Technical impact: partial

3. Oct 19, 2026, 9:19 PM UTCRecord last updated

Affected versions

• Linux Linux

  From 0d76daf2013ce1da20eab5e26bd81d983e1c18fb · fixed in fb080b6f54835d5d4d11ce3122800e6f0f6689e6; From ec624fe740b416fb68d536b37fb8eef46f90b5c2 · fixed in 67d6b00a54446c008f52cf70fc0c2ad0c712f85d; From ec624fe740b416fb68d536b37fb8eef46f90b5c2 · fixed in 2400c4b05d58834b994500a9eec90a37db44187c; From ec624fe740b416fb68d536b37fb8eef46f90b5c2 · fixed in 5c3ae5f6c7c6de73ea9b6a75154fe4ed343e1bac; From ec624fe740b416fb68d536b37fb8eef46f90b5c2 · fixed in b3d835407846134b0d54637c0281b39bebef831d; From ec624fe740b416fb68d536b37fb8eef46f90b5c2 · fixed in f7f45ceb855d9ba1cba594fb3f383255f7013fad; From ec624fe740b416fb68d536b37fb8eef46f90b5c2 · fixed in 9092e15defbe6c7bc241c306093ca9d358a578e7; From 5.15.13 · fixed in 5.15.217

• Linux Linux

  5.16

• KernelLinux

  fixed in 5.15.217; From 5.16.0 · fixed in 6.1.184; fixed in 6.6.145; From 6.2.0 · fixed in 6.12.97; From 6.7.0 · fixed in 6.18.40; From 6.13.0 · fixed in 7.1.5

References 7