# CVE-2026-74688: sctp: clear control chunk transport if it is being removed

> A use-after-free in the Linux kernel SCTP implementation allows attackers to execute arbitrary code or escalate privileges when specific transport removal conditions occur.

- **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:** 22 Aug 2026
- **Updated:** 16 Oct 2026
- **Also known as:** AZL-97196, BELL-CVE-2026-74688, DEBIAN-CVE-2026-74688, GHSA-3vfv-7x6v-8jg6, UBUNTU-CVE-2026-74688

## What is CVE-2026-74688?

CVE-2026-74688 is a critical use after free vulnerability in Linux, published on 22 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:

sctp: clear control chunk transport if it is being removed

sctp_make_heartbeat_ack() caches the destination transport in
chunk->transport without taking a reference. When src_out_of_asoc_ok is
enabled, the HEARTBEAT ACK may remain queued on control_chunk_list instead
of being transmitted immediately.

If the peer transport is removed while the chunk is still queued,
sctp_assoc_rm_peer() drops the transport and schedules it for RCU freeing,
but only clears cached transport pointers in out_chunk_list.  The queued
control chunk therefore retains a dangling transport pointer.

Once an ASCONF_ACK clears the suppression and the queued control chunk is
transmitted, SCTP dereferences the stale transport pointer, leading to a
use-after-free.

Fix this by also clearing chunk->transport for queued control chunks in
control_chunk_list when removing the transport.

## Which versions are affected by CVE-2026-74688?


## How do I fix CVE-2026-74688?

Apply the vendor's patch.

## Is CVE-2026-74688 being exploited?

There is no known exploitation of CVE-2026-74688 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-74688 and fix it if it is affected.

What it is: CVE-2026-74688 is a critical use after free vulnerability in Linux, published on 22 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-2026-74688 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-2026-74688/ (Markdown: https://insights.sbomify.com/CVE-2026-74688/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-74688
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-74688
- OSV: https://osv.dev/vulnerability/CVE-2026-74688

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-74688/
Summaries are generated and may contain mistakes; the official description above is the record.