# CVE-2026-74493: net/smc: fix socket use-after-free during link group termination

> A race condition in the Linux kernel SMC module allows a use-after-free during link group termination, potentially leading to code execution or system crashes.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/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:** Not needed
- **Fix available:** Yes
- **Published:** 15 Aug 2026
- **Updated:** 16 Oct 2026
- **Also known as:** AZL-96326, BELL-CVE-2026-74493, DEBIAN-CVE-2026-74493, GHSA-xhjj-46q7-2hx6, UBUNTU-CVE-2026-74493

## What is CVE-2026-74493?

CVE-2026-74493 is a critical use after free vulnerability in Linux, published on 15 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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

net/smc: fix socket use-after-free during link group termination

__smc_lgr_terminate() drops conns_lock after finding a connection in
lgr->conns_all, but before taking a reference on its socket. The connection
is embedded in the socket, and its registration reference protects it only
while the connection remains in the tree.

A concurrent close can unregister the connection and drop that reference,
freeing the socket before the termination worker reaches sock_hold().

The race is reachable when close overlaps link group termination.
Local stress testing reproduced the use-after-free and KASAN reported:

  BUG: KASAN: slab-use-after-free in __smc_lgr_terminate.part.0 [smc]
  Write of size 4 by task kworker/3:3
  Workqueue: events smc_lgr_terminate_work [smc]
  __smc_lgr_terminate.part.0 [smc]

The socket was allocated by smc_create(), freed through
slab_free_after_rcu_debug(), and was followed by:

  refcount_t: addition on 0; use-after-free.
  __smc_lgr_terminate.part.0 [smc]

Take the socket reference while conns_lock still protects the tree entry.
The unregister path then cannot drop the last reference until termination
has finished using the socket.

## Which versions are affected by CVE-2026-74493?


## How do I fix CVE-2026-74493?

Apply the vendor's patch.

## Is CVE-2026-74493 being exploited?

There is no known exploitation of CVE-2026-74493 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-74493 and fix it if it is affected.

What it is: CVE-2026-74493 is a critical use after free vulnerability in Linux, published on 15 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-74493 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-2026-74493/ (Markdown: https://insights.sbomify.com/CVE-2026-74493/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-74493
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-74493
- OSV: https://osv.dev/vulnerability/CVE-2026-74493

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-74493/
Summaries are generated and may contain mistakes; the official description above is the record.