# CVE-2026-74588: sctp: keep chunk->transport in step with the list it is queued on

> A use-after-free in the Linux kernel SCTP implementation allows remote attackers to cause a denial of service or potentially execute code via crafted SACK packets.

- **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-97232, BELL-CVE-2026-74588, DEBIAN-CVE-2026-74588, GHSA-g275-m9xc-x5q2, UBUNTU-CVE-2026-74588

## What is CVE-2026-74588?

CVE-2026-74588 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: keep chunk->transport in step with the list it is queued on

__sctp_outq_flush_rtx() moves a gap-acked chunk onto another transport's
transmitted list without updating chunk->transport:

	if (chunk->tsn_gap_acked) {
		list_move_tail(&chunk->transmitted_list,
			       &transport->transmitted);
		continue;
	}

The chunk then sits on a live transport's list while chunk->transport still
names a different one.  If that transport is removed - sctp_assoc_rm_peer()
from an ASCONF Delete-IP - sctp_transport_free() RCU-frees it and the chunk
is left with a dangling pointer.  sctp_assoc_rm_peer() scrubs
peer->transmitted and asoc->outqueue.out_chunk_list, but the chunk is on
neither.

The pointer is not followed while tsn_gap_acked is set.  A SACK that
reneges on the TSN clears the flag, and the next SACK reaches

	tchunk->transport->flight_size -= sctp_data_size(tchunk);

inside the freed transport.  KASAN reports a slab-use-after-free read in
sctp_check_transmitted(), freed from sctp_assoc_rm_peer().  Both the
removal and the SACKs come from the association peer.

Set chunk->transport at the move.  The ordinary resend path needs nothing:
it reaches its list_move_tail() only after sctp_packet_append_chunk()
returned SCTP_XMIT_OK, and __sctp_packet_append_chunk() has rebound the
chunk by then.

Discovered by XBOW, triaged by Baul Lee <baul.lee@xbow.com>

## Which versions are affected by CVE-2026-74588?


## How do I fix CVE-2026-74588?

Apply the vendor's patch.

## Is CVE-2026-74588 being exploited?

There is no known exploitation of CVE-2026-74588 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-74588 and fix it if it is affected.

What it is: CVE-2026-74588 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-2026-74588 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-2026-74588/ (Markdown: https://insights.sbomify.com/CVE-2026-74588/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-74588
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-74588
- OSV: https://osv.dev/vulnerability/CVE-2026-74588

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-74588/
Summaries are generated and may contain mistakes; the official description above is the record.