# CVE-2021-47077: scsi: qedf: Add pointer checks in qedf_update_link_speed()

> A missing null pointer check in the Linux kernel's qedf driver can cause a system crash when updating link speed.

- **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:** 1 Mar 2024
- **Updated:** 11 May 2026
- **Also known as:** DEBIAN-CVE-2021-47077, GHSA-xcfc-r834-76g4, UBUNTU-CVE-2021-47077

## What is CVE-2021-47077?

CVE-2021-47077 is a medium-severity vulnerability in Linux kernel, published on 1 Mar 2024. 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:

scsi: qedf: Add pointer checks in qedf_update_link_speed()

The following trace was observed:

 [   14.042059] Call Trace:
 [   14.042061]  <IRQ>
 [   14.042068]  qedf_link_update+0x144/0x1f0 [qedf]
 [   14.042117]  qed_link_update+0x5c/0x80 [qed]
 [   14.042135]  qed_mcp_handle_link_change+0x2d2/0x410 [qed]
 [   14.042155]  ? qed_set_ptt+0x70/0x80 [qed]
 [   14.042170]  ? qed_set_ptt+0x70/0x80 [qed]
 [   14.042186]  ? qed_rd+0x13/0x40 [qed]
 [   14.042205]  qed_mcp_handle_events+0x437/0x690 [qed]
 [   14.042221]  ? qed_set_ptt+0x70/0x80 [qed]
 [   14.042239]  qed_int_sp_dpc+0x3a6/0x3e0 [qed]
 [   14.042245]  tasklet_action_common.isra.14+0x5a/0x100
 [   14.042250]  __do_softirq+0xe4/0x2f8
 [   14.042253]  irq_exit+0xf7/0x100
 [   14.042255]  do_IRQ+0x7f/0xd0
 [   14.042257]  common_interrupt+0xf/0xf
 [   14.042259]  </IRQ>

API qedf_link_update() is getting called from QED but by that time
shost_data is not initialised. This results in a NULL pointer dereference
when we try to dereference shost_data while updating supported_speeds.

Add a NULL pointer check before dereferencing shost_data.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2021-47077?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2021-47077?

Apply the vendor's patch.

## Is CVE-2021-47077 being exploited?

There is no known exploitation of CVE-2021-47077 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-2021-47077 and fix it if it is affected.

What it is: CVE-2021-47077 is a medium-severity vulnerability in Linux kernel, published on 1 Mar 2024. 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-2021-47077 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-2021-47077/ (Markdown: https://insights.sbomify.com/CVE-2021-47077/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-47077
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-47077
- OSV: https://osv.dev/vulnerability/CVE-2021-47077

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-47077/
Summaries are generated and may contain mistakes; the official description above is the record.