Bug 2562684 (CVE-2026-99201)

Summary: CVE-2026-99201 kernel: kernel: Information disclosure via netlink network namespace pointer hashing
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: low Docs Contact:
Priority: low    
Version: unspecifiedCC: akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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Fixed In Version: Doc Type: ---
Doc Text:
A flaw was found in the Linux kernel's netlink subsystem. An unprivileged local user can exploit this vulnerability by manipulating netlink sockets with chosen port identifiers and observing exposed table bucket order. This flaw results in an information disclosure, allowing an attacker to infer sensitive internal kernel memory addresses and potentially bypass Kernel Address Space Layout Randomization (KASLR).
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-10-28 10:49:04 UTC 
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.