CVE-2026-64563

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Use-After-Free in Linux Kernel rhashtable

Publication date: 2026-08-04

Last updated on: 2026-11-03

Assigner: kernel.org

Description

In the Linux kernel, the following vulnerability has been resolved: rhashtable: clear stale iter->p on table restart rhashtable_walk_start_check() has two restart paths when resuming a walk. When iter->walker.tbl is valid, it re-validates iter->p against the table and sets iter->p = NULL if the object is gone. When iter->walker.tbl is NULL (table was freed during resize), it resets slot and skip but forgets to clear iter->p. rhashtable_walk_next() then dereferences the stale iter->p, reading freed memory. This is a use-after-free. Any caller that does multi-fragment rhashtable walks across walk_stop/walk_start boundaries is affected. Concrete cases include netlink_diag (__netlink_diag_dump in net/netlink/diag.c) and TIPC (tipc_nl_sk_walk in net/tipc/socket.c). Crash stack (netlink_diag): BUG: KASAN: slab-use-after-free in rhashtable_walk_next+0x365/0x3c0 Read of size 8 at addr ffff88801a9d2438 (freed kmalloc-2k, offset 1080) Call Trace: rhashtable_walk_next+0x365/0x3c0 (lib/rhashtable.c:1016) __netlink_diag_dump+0x160/0x760 (net/netlink/diag.c:122) netlink_diag_dump+0xc2/0x240 netlink_dump+0x5bc/0x1270 netlink_recvmsg+0x7a3/0x980 sock_recvmsg+0x1bc/0x200 __sys_recvfrom+0x1d4/0x2c0

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Meta Information

Published

2026-08-04

Last Modified

2026-11-03

Generated

2026-11-08

AI Q&A

2026-08-04

EPSS Evaluated

2026-11-07

NVD

CVE-2026-64563

EUVD

EUVD-2026-52604

Affected Vendors & Products

Vendor	Product	Version / Range
linux_kernel	rhashtable	*

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-416	The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.

Attack-Flow Graph

Executive Summary

This is a use-after-free vulnerability in the Linux kernel's rhashtable implementation. It occurs when rhashtable_walk_start_check() resumes a walk after a table resize. If the table was freed during resize, the code resets slot and skip but fails to clear iter->p. Later, rhashtable_walk_next() dereferences this stale pointer, reading freed memory.

Detection Guidance

This vulnerability is specific to the Linux kernel's rhashtable implementation and may not have direct detection commands. Monitor kernel logs for slab-use-after-free errors or crashes in netlink_diag or TIPC modules. Check for kernel oops or KASAN reports indicating use-after-free in rhashtable_walk_next.

Impact Analysis

This vulnerability can cause system crashes due to memory corruption. Attackers could exploit it to execute arbitrary code with kernel privileges, leading to full system compromise. Systems using affected kernel features like netlink_diag or TIPC are particularly at risk.

Compliance Impact

This vulnerability is a use-after-free flaw in the Linux kernel's rhashtable implementation that could lead to memory corruption or crashes. While it does not directly impact data privacy or security controls required by GDPR or HIPAA, it could potentially cause system instability or denial-of-service conditions if exploited. Such conditions might indirectly affect compliance by disrupting data processing or access controls.

Mitigation Strategies

Apply the latest kernel patches from your Linux distribution to resolve the rhashtable issue. If immediate patching is not possible, consider disabling affected modules like netlink_diag or TIPC if they are not critical. Monitor system stability and kernel logs for signs of exploitation.

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