VulnerabilityPublished 28 Oct 2026

CVE-2026-99201: Linux kernel · netlink: avoid hashing the network namespace pointer

Affects Linux kernelSource CVE Database V5

Not known to be exploited · fixed in f88bb3606e4bd11ee035b682cddc2999e604609a : update Linux kernel when convenient.

Data as of 28 Oct 2026, 10:58 UTC

Severity

Unrated

Rated by Threat Radar · CVSS not yet scored by NVD

Patch: Available – fixed in f88bb3606e4bd11ee035b682cddc2999e604609a, bdd55b8a8acbf6b4840ab420eb6a63774bf4593b, 078deff25f8a849ecd1c3fe17b1e473b1cf44f28

Exploitation evidence

Disclosed: evidence found.
CVE published 28 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade Linux kernel to f88bb3606e4bd11ee035b682cddc2999e604609a, bdd55b8a8acbf6b4840ab420eb6a63774bf4593b or 078deff25f8a849ecd1c3fe17b1e473b1cf44f28.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ c428ecd1a21f1457ca3beb4df71b8a079c410e41, < f88bb3606e4bd11ee035b682cddc2999e604609a	Fixed in f88bb3606e4bd11ee035b682cddc2999e604609a
LinuxLinux	Affected ≥ c428ecd1a21f1457ca3beb4df71b8a079c410e41, < bdd55b8a8acbf6b4840ab420eb6a63774bf4593b	Fixed in bdd55b8a8acbf6b4840ab420eb6a63774bf4593b
LinuxLinux	Affected ≥ c428ecd1a21f1457ca3beb4df71b8a079c410e41, < 078deff25f8a849ecd1c3fe17b1e473b1cf44f28	Fixed in 078deff25f8a849ecd1c3fe17b1e473b1cf44f28
LinuxLinux	Affected =4.1	Fixed in–

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.

References

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