CVE Catalog

CVE-2026-98284

Low risk· EPSS 5%
Published: Updated: Translated: NVD NIST

Exploitation Probability (EPSS)

Low risk
0.16%

5th percentile - higher than 5% of all known CVEs

Summary

In the Linux kernel, a vulnerability was found in the netlink subsystem where netlink_realloc_groups() can free the old group bitmap before lockless readers finish using it. Two read paths (sk_diag_dump_groups() and /proc/net/netlink) can access freed memory, leading to use-after-free or out-of-bounds read.

Risk Assessment

An attacker could exploit this vulnerability to escalate privileges or leak kernel memory, compromising system confidentiality and integrity.

Recommendation

Immediately update the Linux kernel to a version containing the fix that changes bitmap allocation and freeing to use RCU grace period and proper publication ordering.

Other vulnerabilities in Linux kernel

See all
Original NVD description (English source)

In the Linux kernel, the following vulnerability has been resolved: netlink: do not free nlk->groups while lockless readers can use it netlink_realloc_groups() uses krealloc() under netlink_table_grab(). Whenever NLGRPSZ(groups) lands in a different kmalloc bucket, the old bitmap is freed immediately. Two readers of nlk->groups / nlk->ngroups do not hold the netlink table lock: 1) sk_diag_dump_groups(). Hashed (bound) sockets are dumped from the rhashtable walk in __netlink_diag_dump(), which only holds RCU. Only the mc_list part of the dump takes nl_table_lock. 2) netlink_native_seq_show() (/proc/net/netlink), whose walk has been lockless since commit 21e4902aea80 ("netlink: Lockless lookup with RCU grace period in socket release"). Both can read a freed buffer, and sk_diag_dump_groups() can also read past the end of the old (smaller) buffer if it happens to load the old @groups pointer together with the new @ngroups value, copying the result into a NETLINK_DIAG_GROUPS attribute. This is the same class of bug that commit f773608026ee ("netlink: access nlk groups safely in netlink bind and getname") fixed for bind() and getname(); these two readers were missed. Simply grabbing the table lock in sk_diag_dump_groups() is not an option, because it is also called with nl_table_lock already held from the mc_list section of the dump. Make the lockless readers safe instead: - Allocate a new bitmap and free the old one after an RCU grace period, instead of relying on the implicit kfree() done by krealloc(). - Publish @groups before @ngroups, both with release semantics, and have the lockless readers load @ngroups first. A reader can then never pair the new (bigger) size with the old (smaller) buffer, and a reader picking up the new pointer while still seeing the old size is guaranteed to see the initialized bitmap. netlink_realloc_groups() is called from process context (bind() and setsockopt()), so kfree_rcu_mightsleep() can be used, once the table has been released.

Vulnerability data from NVD (NIST) · CISA KEV · EPSS