VulnerabilityPublished 28 Oct 2026

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

Source GCVE Database

Authoritative record:CVE-2026-99201

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

Data as of 28 Oct 2026, 13:30 UTC

Severity

Medium

Rated Medium by Threat Radar's AI analysis · 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.

ghsa-q237-q634-6984

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–

AI-suggested

A fix has been implemented in the Linux kernel to replace the hashing of raw network namespace pointers with the use of the namespace's unique net_cookie. Users and administrators should apply the official kernel updates that include this fix. The change is backportable to kernel versions 5.15 and later. No additional mitigation steps are indicated beyond applying the patch.

Description

A vulnerability in the Linux kernel's netlink subsystem allowed an unprivileged user to infer kernel memory layout details by exploiting how network namespace pointers were hashed. This could enable recovery of the address of init_net, a kernel structure. The issue was fixed by replacing the use of raw network namespace pointers with a unique, non-address net_cookie value in hash keys, preventing information leakage. The fix is compatible with older stable kernels and preserves namespace separation without changing public table walkers.

Impact

An unprivileged user could leverage this vulnerability to infer kernel memory layout information, specifically the address of init_net, which could aid in further kernel exploitation techniques. However, there is no indication of direct code execution or privilege escalation solely from this issue. No known exploits in the wild have been reported.

Summary

The Linux kernel netlink rhashtable key previously included a raw struct net pointer and a user-controlled port ID. Because /proc/net/netlink and socket diagnostics expose the table's bucket order, an unprivileged user could bind and rebind NETLINK_USERSOCK port IDs to distinguish equal buckets and recover low bits of the Jenkins hash. This hash, combined with a 32-bit seed and limited kernel-image slide range, allowed offline recovery of the init_net address. The vulnerability was mitigated by replacing the raw network namespace pointer with the namespace's unique net_cookie in the hash key. This net_cookie is assigned before per-net initializers run and remains constant for the namespace's lifetime, ensuring safe and consistent hashing and lookup operations under RCU synchronization. The fix is straightforward to backport to Linux kernel versions 5.15 and later.

References

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