# CVE-2026-64563: rhashtable: clear stale iter->p on table restart

> A use-after-free in the Linux kernel rhashtable allows attackers to cause a crash or potentially execute code via netlink or TIPC sockets.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 4 Aug 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-94371, BELL-CVE-2026-64563, DEBIAN-CVE-2026-64563, GHSA-8g97-85g6-9whw, UBUNTU-CVE-2026-64563

## What is CVE-2026-64563?

CVE-2026-64563 is a high-severity use after free vulnerability in Linux, published on 4 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official 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

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2026-64563?


## How do I fix CVE-2026-64563?

Apply the vendor's patch.

## Is CVE-2026-64563 being exploited?

There is no known exploitation of CVE-2026-64563 in the wild and no public exploit code.

Public exploit code:

- 关于CVE-2026-64563未完全验证的一种利用思路 (github_poc): https://github.com/guard-wait/CVE-2026-64563_EXP

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-64563 and fix it if it is affected.

What it is: CVE-2026-64563 is a high-severity use after free vulnerability in Linux, published on 4 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-64563 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-64563/ (Markdown: https://insights.sbomify.com/CVE-2026-64563/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-64563
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-64563
- OSV: https://osv.dev/vulnerability/CVE-2026-64563

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-64563/
Summaries are generated and may contain mistakes; the official description above is the record.