What’s Vulnerable › Vulnerabilities

CVE-2026-72057: net/sched: act_ct: preserve tc_skb_cb across defragmentation

• Severity: high (CVSS 8.2 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.6% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-15 · updated 2026-10-19
• Weakness: CWE-662

Description

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().

Affected products

• Linux kernel: from 5.15.13 before 5.15.217; 5.16 — fixed in 5.15.217, 7.2

How to fix

Upgrade to a fixed version: Linux kernel 5.15.217, 7.2. Check the vendor advisory for mitigations.

References

• https://git.kernel.org/stable/c/2400c4b05d58834b994500a9eec90a37db44187c
• https://git.kernel.org/stable/c/5c3ae5f6c7c6de73ea9b6a75154fe4ed343e1bac
• https://git.kernel.org/stable/c/67d6b00a54446c008f52cf70fc0c2ad0c712f85d
• https://git.kernel.org/stable/c/9092e15defbe6c7bc241c306093ca9d358a578e7
• https://git.kernel.org/stable/c/b3d835407846134b0d54637c0281b39bebef831d
• https://git.kernel.org/stable/c/f7f45ceb855d9ba1cba594fb3f383255f7013fad
• https://git.kernel.org/stable/c/fb080b6f54835d5d4d11ce3122800e6f0f6689e6

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