# CVE-2026-72398: sctp: add INIT verification after cookie unpacking

> Attackers can bypass SCTP INIT verification when cookie authentication is disabled, potentially leading to code execution or denial of service.

- **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:** 21 Oct 2026
- **Also known as:** AZL-96171, BELL-CVE-2026-72398, DEBIAN-CVE-2026-72398, GHSA-59hc-5687-r27h, UBUNTU-CVE-2026-72398

## What is CVE-2026-72398?

CVE-2026-72398 is a critical missing authorization 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:

sctp: add INIT verification after cookie unpacking

In SCTP handshake, the INIT chunk is initially processed by the server
and embedded into the cookie carried in INIT-ACK. The client then
returns this cookie via COOKIE-ECHO, where the server unpacks it and
reconstructs the original INIT chunk.

When cookie authentication is enabled, the cookie contents are protected
against tampering, so reusing the unpacked INIT without re-verification
is safe.

However, when cookie authentication is disabled, the reconstructed INIT
can no longer be trusted. In this case, the INIT must be explicitly
validated after unpacking to avoid processing potentially tampered data.

Add sctp_verify_init() checks after cookie unpacking in COOKIE-ECHO
processing paths (sctp_sf_do_5_1D_ce() and sctp_sf_do_5_2_4_dupcook())
when cookie_auth_enable is disabled. On failure, the new association is
freed and the packet is discarded.

Also tighten cookie validation in sctp_unpack_cookie() by verifying the
embedded chunk type is SCTP_CID_INIT before treating it as an INIT
chunk.

Finally, update sctp_verify_init() to validate parameter bounds using
the actual embedded INIT length instead of chunk->chunk_end, since the
INIT stored in COOKIE-ECHO may not span the entire chunk buffer.

## Which versions are affected by CVE-2026-72398?


## How do I fix CVE-2026-72398?

Apply the vendor's patch.

## Is CVE-2026-72398 being exploited?

There is no known exploitation of CVE-2026-72398 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-72398 and fix it if it is affected.

What it is: CVE-2026-72398 is a critical missing authorization 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-2026-72398 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-2026-72398/ (Markdown: https://insights.sbomify.com/CVE-2026-72398/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-72398
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-72398
- OSV: https://osv.dev/vulnerability/CVE-2026-72398

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-72398/
Summaries are generated and may contain mistakes; the official description above is the record.