# CVE-2021-47397: sctp: break out if skb_header_pointer returns NULL in sctp_rcv_ootb

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

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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:** 21 May 2024
- **Updated:** 5 Aug 2026
- **Also known as:** DEBIAN-CVE-2021-47397, GHSA-v8p3-mfrc-9v8j, UBUNTU-CVE-2021-47397

## What is CVE-2021-47397?

CVE-2021-47397 is a high-severity vulnerability in Linux kernel, published on 21 May 2024. 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: break out if skb_header_pointer returns NULL in sctp_rcv_ootb

We should always check if skb_header_pointer's return is NULL before
using it, otherwise it may cause null-ptr-deref, as syzbot reported:

  KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
  RIP: 0010:sctp_rcv_ootb net/sctp/input.c:705 [inline]
  RIP: 0010:sctp_rcv+0x1d84/0x3220 net/sctp/input.c:196
  Call Trace:
  <IRQ>
   sctp6_rcv+0x38/0x60 net/sctp/ipv6.c:1109
   ip6_protocol_deliver_rcu+0x2e9/0x1ca0 net/ipv6/ip6_input.c:422
   ip6_input_finish+0x62/0x170 net/ipv6/ip6_input.c:463
   NF_HOOK include/linux/netfilter.h:307 [inline]
   NF_HOOK include/linux/netfilter.h:301 [inline]
   ip6_input+0x9c/0xd0 net/ipv6/ip6_input.c:472
   dst_input include/net/dst.h:460 [inline]
   ip6_rcv_finish net/ipv6/ip6_input.c:76 [inline]
   NF_HOOK include/linux/netfilter.h:307 [inline]
   NF_HOOK include/linux/netfilter.h:301 [inline]
   ipv6_rcv+0x28c/0x3c0 net/ipv6/ip6_input.c:297

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2021-47397?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2021-47397?

Apply the vendor's patch.

## Is CVE-2021-47397 being exploited?

There is no known exploitation of CVE-2021-47397 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-2021-47397 and fix it if it is affected.

What it is: CVE-2021-47397 is a high-severity vulnerability in Linux kernel, published on 21 May 2024. 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-2021-47397 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-2021-47397/ (Markdown: https://insights.sbomify.com/CVE-2021-47397/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-47397
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-47397
- OSV: https://osv.dev/vulnerability/CVE-2021-47397

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-47397/
Summaries are generated and may contain mistakes; the official description above is the record.