# CVE-2026-89479: sctp: stop processing a packet once its association is deleted

> A use-after-free in the Linux kernel SCTP implementation allows attackers to cause denial of service or execute code via crafted 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:** 11 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-100410, BELL-CVE-2026-89479, DEBIAN-CVE-2026-89479, GHSA-2f22-4vgf-p33p, UBUNTU-CVE-2026-89479

## What is CVE-2026-89479?

CVE-2026-89479 is a critical use after free vulnerability in Linux, published on 11 Sep 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: stop processing a packet once its association is deleted

sctp_endpoint_bh_rcv() looks the association up only when chunk->asoc is
NULL, and caches the result in chunk->asoc and chunk->transport without
taking a reference.

A packet that matches no association is handed to the endpoint, so a peer
can bundle COOKIE ECHO, SHUTDOWN and SHUTDOWN ACK in one packet. The
COOKIE ECHO creates the association, the SHUTDOWN chunk caches it, and
with the outqueue empty the SHUTDOWN ACK reaches sctp_sf_do_9_2_final(),
so the association and its transports are freed.

The endpoint loop has no counterpart to the asoc->base.dead check in
sctp_assoc_bh_rcv(). The next chunk writes to last_time_heard in the freed
transport and is then passed to sctp_do_sm() with the freed association.
The transport is freed through RCU, so this needs the packet to come off
the socket backlog, where the loop runs in task context.

The endpoint loop cannot do the same check: it holds no reference on the
association, so reading asoc->base.dead would itself be a use-after-free.
Mark the packet for discard in the command interpreter, just before it
deletes the association. That is also before sctp_inq_free() releases the
chunk on the association receive path.

sctp_sf_do_5_2_4_dupcook() issues SCTP_CMD_DELETE_TCB for the temporary
association, while the one the packet belongs to stays alive. A restarting
peer can bundle DATA behind its COOKIE ECHO, so compare against
chunk->asoc and leave that case alone.

## Which versions are affected by CVE-2026-89479?


## How do I fix CVE-2026-89479?

Apply the vendor's patch.

## Is CVE-2026-89479 being exploited?

There is no known exploitation of CVE-2026-89479 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89479 and fix it if it is affected.

What it is: CVE-2026-89479 is a critical use after free vulnerability in Linux, published on 11 Sep 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-2026-89479 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-2026-89479/ (Markdown: https://insights.sbomify.com/CVE-2026-89479/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89479
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89479
- OSV: https://osv.dev/vulnerability/CVE-2026-89479

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89479/
Summaries are generated and may contain mistakes; the official description above is the record.