CVE-2026-99201: Linux Vulnerability

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.

Metrics

EPSS Probability

0.16%

5.2th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

Vendor	Product	Versions
Linux	Linux	>= c428ecd1a21f1457ca3beb4df71b8a079c410e41, < c61431f3b8c9824e9848a0308054f92b27fa7794; >= c428ecd1a21f1457ca3beb4df71b8a079c410e41, < f8d2690f3c5dfad1fc306f6d5d84a1d3176c3af9; >= c428ecd1a21f1457ca3beb4df71b8a079c410e41, < c03fb9c4be3b2dd0996d91e54f65407f7f475238; >= c428ecd1a21f1457ca3beb4df71b8a079c410e41, < 41a2f69f091b0765f17890d8ac04852c12f25cf6; >= c428ecd1a21f1457ca3beb4df71b8a079c410e41, < 18edcb9945118beb7a1b64a31a7370ecab485a79; >= c428ecd1a21f1457ca3beb4df71b8a079c410e41, < bdd55b8a8acbf6b4840ab420eb6a63774bf4593b; >= c428ecd1a21f1457ca3beb4df71b8a079c410e41, < 078deff25f8a849ecd1c3fe17b1e473b1cf44f28; >= c428ecd1a21f1457ca3beb4df71b8a079c410e41, < f88bb3606e4bd11ee035b682cddc2999e604609a
Linux	Linux	4.1

References

Timeline

Published: Oct 28, 2026
Last Modified: Oct 30, 2026
Status: Received

Frequently Asked Questions

What is CVE-2026-99201?

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.

How severe is CVE-2026-99201?

Severity scoring for CVE-2026-99201 is pending analysis. The EPSS model estimates a 0.16% probability of exploitation in the next 30 days.

How do I fix CVE-2026-99201?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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