# CVE-2026-23125: sctp: move SCTP_CMD_ASSOC_SHKEY right after SCTP_CMD_PEER_INIT

> A null pointer dereference in the Linux kernel SCTP implementation allows remote attackers to cause a denial of service via crafted network packets.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 14 Feb 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-77751, BELL-CVE-2026-23125, DEBIAN-CVE-2026-23125, GHSA-crj3-7xqp-x3m2, ROOT-OS-UBUNTU-2204-CVE-2026-23125, ROOT-OS-UBUNTU-2404-CVE-2026-23125, UBUNTU-CVE-2026-23125

## What is CVE-2026-23125?

CVE-2026-23125 is a medium-severity vulnerability in Linux kernel, published on 14 Feb 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

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

sctp: move SCTP_CMD_ASSOC_SHKEY right after SCTP_CMD_PEER_INIT

A null-ptr-deref was reported in the SCTP transmit path when SCTP-AUTH key
initialization fails:

  ==================================================================
  KASAN: null-ptr-deref in range [0x0000000000000018-0x000000000000001f]
  CPU: 0 PID: 16 Comm: ksoftirqd/0 Tainted: G W 6.6.0 #2
  RIP: 0010:sctp_packet_bundle_auth net/sctp/output.c:264 [inline]
  RIP: 0010:sctp_packet_append_chunk+0xb36/0x1260 net/sctp/output.c:401
  Call Trace:

  sctp_packet_transmit_chunk+0x31/0x250 net/sctp/output.c:189
  sctp_outq_flush_data+0xa29/0x26d0 net/sctp/outqueue.c:1111
  sctp_outq_flush+0xc80/0x1240 net/sctp/outqueue.c:1217
  sctp_cmd_interpreter.isra.0+0x19a5/0x62c0 net/sctp/sm_sideeffect.c:1787
  sctp_side_effects net/sctp/sm_sideeffect.c:1198 [inline]
  sctp_do_sm+0x1a3/0x670 net/sctp/sm_sideeffect.c:1169
  sctp_assoc_bh_rcv+0x33e/0x640 net/sctp/associola.c:1052
  sctp_inq_push+0x1dd/0x280 net/sctp/inqueue.c:88
  sctp_rcv+0x11ae/0x3100 net/sctp/input.c:243
  sctp6_rcv+0x3d/0x60 net/sctp/ipv6.c:1127

The issue is triggered when sctp_auth_asoc_init_active_key() fails in
sctp_sf_do_5_1C_ack() while processing an INIT_ACK. In this case, the
command sequence is currently:

- SCTP_CMD_PEER_INIT
- SCTP_CMD_TIMER_STOP (T1_INIT)
- SCTP_CMD_TIMER_START (T1_COOKIE)
- SCTP_CMD_NEW_STATE (COOKIE_ECHOED)
- SCTP_CMD_ASSOC_SHKEY
- SCTP_CMD_GEN_COOKIE_ECHO

If SCTP_CMD_ASSOC_SHKEY fails, asoc->shkey remains NULL, while
asoc->peer.auth_capable and asoc->peer.peer_chunks have already been set by
SCTP_CMD_PEER_INIT. This allows a DATA chunk with auth = 1 and shkey = NULL
to be queued by sctp_datamsg_from_user().

Since command interpretation stops on failure, no COOKIE_ECHO should been
sent via SCTP_CMD_GEN_COOKIE_ECHO. However, the T1_COOKIE timer has already
been started, and it may enqueue a COOKIE_ECHO into the outqueue later. As
a result, the DATA chunk can be transmitted together with the COOKIE_ECHO
in sctp_outq_flush_data(), leading to the observed issue.

Similar to the other places where it calls sctp_auth_asoc_init_active_key()
right after sctp_process_init(), this patch moves the SCTP_CMD_ASSOC_SHKEY
immediately after SCTP_CMD_PEER_INIT, before stopping T1_INIT and starting
T1_COOKIE. This ensures that if shared key generation fails, authenticated
DATA cannot be sent. It also allows the T1_INIT timer to retransmit INIT,
giving the client another chance to process INIT_ACK and retry key setup.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2026-23125?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-23125?

Apply the vendor's patch.

## Is CVE-2026-23125 being exploited?

There is no known exploitation of CVE-2026-23125 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-23125 and fix it if it is affected.

What it is: CVE-2026-23125 is a medium-severity vulnerability in Linux kernel, published on 14 Feb 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-23125 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2026-23125/ (Markdown: https://insights.sbomify.com/CVE-2026-23125/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-23125
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-23125
- OSV: https://osv.dev/vulnerability/CVE-2026-23125

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-23125/
Summaries are generated and may contain mistakes; the official description above is the record.