# CVE-2026-97583: afs: Clear stale peer app data after address list changes

> A use-after-free in the Linux kernel AFS module allows attackers to cause a system crash or potentially execute code via crafted network packets.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 25 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-97583, DEBIAN-CVE-2026-97583, GHSA-477v-9mhf-xmx8, UBUNTU-CVE-2026-97583

## What is CVE-2026-97583?

CVE-2026-97583 is a high-severity use after free vulnerability in Linux, published on 25 Sep 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

afs: Clear stale peer app data after address list changes

afs_fs_probe_fileserver() fetches the current endpoint state under
server->fs_lock, but leaves old_alist as NULL.  Consequently,
afs_set_peer_appdata() treats every address list replacement as initial
setup and only binds the new peers; it never unbinds peers removed from
the old list.

An address refresh can therefore proceed as follows.  CPU 0 replaces
server S's list and drops Pold without clearing Pold->app_data.  The
server destroyer then clears only S's current peers and lets S reach its
RCU callback.  After the callback frees S, CPU 1 handles a callback
through an RxRPC connection that still pins Pold, reads Pold->app_data,
and calls afs_use_server() on the freed object.

KASAN reported:

  BUG: KASAN: slab-use-after-free in afs_find_server+0x3c/0xa0
  Read of size 4 at addr ffff8881013e1af0 by task krxrpcio/7001/74
  Call Trace:
   afs_find_server+0x3c/0xa0
   afs_rx_new_call+0x15c/0x390
   rxrpc_new_incoming_call+0x97c/0x1730
   rxrpc_input_packet.constprop.0+0xd03/0xec0
   rxrpc_io_thread+0x967/0x1640
  Allocated by task 93:
   afs_lookup_server+0x1a7/0x14c0
   afs_alloc_server_list+0x43f/0xb60
   afs_create_volume+0x923/0x1490
   afs_get_tree+0x1c6/0x10a0
  Freed by task 0:
   kfree+0x131/0x3c0
   rcu_core+0x50a/0x1850
  Last potentially related work creation:
   __call_rcu_common.constprop.0+0x71/0xa10
   afs_put_server+0x213/0x2b0

Preserve old->addresses for the peer app-data update so that removed
peers are cleared before the endpoint state is replaced.  Also advance
both cursors when the old and new lists share a peer; activating the
old/new comparison without this would otherwise loop forever on the
shared entry.

## Which versions are affected by CVE-2026-97583?


## How do I fix CVE-2026-97583?

Apply the vendor's patch.

## Is CVE-2026-97583 being exploited?

There is no known exploitation of CVE-2026-97583 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-97583 and fix it if it is affected.

What it is: CVE-2026-97583 is a high-severity use after free vulnerability in Linux, published on 25 Sep 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-97583 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-2026-97583/ (Markdown: https://insights.sbomify.com/CVE-2026-97583/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-97583
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-97583
- OSV: https://osv.dev/vulnerability/CVE-2026-97583

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-97583/
Summaries are generated and may contain mistakes; the official description above is the record.