CVE-2026-64563: rhashtable: clear stale iter->p on table restart
In the Linux kernel, the following vulnerability has been resolved:
rhashtable: clear stale iter->p on table restart
rhashtablewalkstartcheck() 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.
rhashtablewalknext() then dereferences the stale iter->p, reading freed memory. This is a use-after-free.
Any caller that does multi-fragment rhashtable walks across walkstop/walkstart boundaries is affected. Concrete cases include netlinkdiag (netlinkdiagdump in net/netlink/diag.c) and TIPC (tipcnlskwalk in net/tipc/socket.c).
Crash stack (netlinkdiag): BUG: KASAN: slab-use-after-free in rhashtablewalknext+0x365/0x3c0 Read of size 8 at addr ffff88801a9d2438 (freed kmalloc-2k, offset 1080) Call Trace: rhashtablewalknext+0x365/0x3c0 (lib/rhashtable.c:1016) netlinkdiagdump+0x160/0x760 (net/netlink/diag.c:122) netlinkdiagdump+0xc2/0x240 netlinkdump+0x5bc/0x1270 netlinkrecvmsg+0x7a3/0x980 sockrecvmsg+0x1bc/0x200 sysrecvfrom+0x1d4/0x2c0
Other sources
In the Linux kernel, the following vulnerability has been resolved:
rhashtable: clear stale iter-p on table restart
rhashtablewalkstartcheck() 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.
rhashtablewalknext() then dereferences the stale iter-p, reading freed memory. This is a use-after-free.
Any caller that does multi-fragment rhashtable walks across walkstop/walkstart boundaries is affected. Concrete cases include netlinkdiag (netlinkdiagdump in net/netlink/diag.c) and TIPC (tipcnlskwalk in net/tipc/socket.c).
Crash stack (netlinkdiag): BUG: KASAN: slab-use-after-free in rhashtablewalknext+0x365/0x3c0 Read of size 8 at addr ffff88801a9d2438 (freed kmalloc-2k, offset 1080) Call Trace: rhashtablewalknext+0x365/0x3c0 (lib/rhashtable.c:1016) netlinkdiagdump+0x160/0x760 (net/netlink/diag.c:122) netlinkdiagdump+0xc2/0x240 netlinkdump+0x5bc/0x1270 netlinkrecvmsg+0x7a3/0x980 sockrecvmsg+0x1bc/0x200 sysrecvfrom+0x1d4/0x2c0
— IBM
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 6.6.152.1-1 - Upgrade
Upgrade
Linux kernelto a version that resolves this vulnerability.Patch rhashtable: clear stale iter->p on table restart
Event History
Frequently Asked Questions
What is the severity of CVE-2026-64563?
The severity of CVE-2026-64563 is rated at 37.
How does CVE-2026-64563 affect the Linux kernel?
CVE-2026-64563 affects the Linux kernel by allowing for potential use-after-free vulnerabilities within the rhashtable implementation.
How do I fix CVE-2026-64563?
To fix CVE-2026-64563, update your Linux kernel to the latest version where the vulnerability has been patched.
What components are impacted by CVE-2026-64563?
CVE-2026-64563 impacts the rhashtable component of the Linux kernel.
What kernel versions are affected by CVE-2026-64563?
CVE-2026-64563 affects multiple versions of the Linux kernel prior to the fix being applied in the release.