# CVE-2026-99128: sctp: validate chunk length in the inqueue parser


- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 28 Oct 2026
- **Updated:** 28 Oct 2026
- **Also known as:** AZL-111239, BELL-CVE-2026-99128, DEBIAN-CVE-2026-99128, GHSA-c382-phc9-mxqc, UBUNTU-CVE-2026-99128

## What is CVE-2026-99128?

CVE-2026-99128 is a vulnerability in Linux, published on 28 Oct 2026. 

### Official description

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

sctp: validate chunk length in the inqueue parser

SCTP chunks always include a four-byte generic header, but
sctp_inq_pop() currently accepts shorter declared lengths. A zero-length
chunk leaves chunk_end at the current header.

When ASCONF is covered by the association's SCTP-AUTH policy,
sctp_assoc_bh_rcv() can continue before the state machine performs its
normal chunk-length check. sctp_inq_pop() then returns the same malformed
chunk repeatedly and the receive softirq can lock up.

A remote SCTP peer can trigger this after establishing an association on
a kernel built with CONFIG_IP_SCTP and configured with
net.sctp.addip_enable=1 and net.sctp.auth_enable=1. The reproducer did
not require application credentials, a shared SCTP AUTH key, or
net.sctp.addip_noauth_enable=1.

On commit f967455fb2a5 ("seg6: reset IP6CB after IPv6 decapsulation"),
one zero-length ASCONF caused repeated
watchdog soft-lockup reports in a two-vCPU KVM guest. All 3 pre-trigger
health probes succeeded, while 36 of 37 post-trigger probes failed. With
this change, all 37 post-trigger probes succeeded and no equivalent
soft-lockup signature appeared.

Reject chunks shorter than the generic SCTP header at the shared inqueue
parser boundary. Mark the packet for discard before either caller can
continue processing it, while preserving the four-byte generic minimum.
Declared-length 1 through 4 controls and kernel-generated ASCONF traffic
remained healthy. The patched sctp_hello selftest passed for IPv4 and
IPv6.

The complete private reproducer and validation evidence are available
directly to maintainers on request.

## Which versions are affected by CVE-2026-99128?


## How do I fix CVE-2026-99128?

Upgrade to a fixed version.

## Is CVE-2026-99128 being exploited?

There is no known exploitation of CVE-2026-99128 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-99128 and fix it if it is affected.

What it is: CVE-2026-99128 is a vulnerability in Linux, published on 28 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-99128 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-2026-99128/ (Markdown: https://insights.sbomify.com/CVE-2026-99128/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-99128
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-99128
- OSV: https://osv.dev/vulnerability/CVE-2026-99128

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-99128/
Summaries are generated and may contain mistakes; the official description above is the record.