# CVE-2021-20286: Denial of service in libnbd

> An assertion failure in libnbd allows attackers to cause a denial of service, requiring updates to the library.

- **Severity:** Low 2.7 (`CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 15 Mar 2021
- **Updated:** 3 Aug 2024
- **Also known as:** AZL-7265, DEBIAN-CVE-2021-20286, GHSA-r4rf-vx7w-8692, SUSE-SU-2021:2274-1, UBUNTU-CVE-2021-20286, openSUSE-SU-2021:2274-1, openSUSE-SU-2024:10961-1

## What is CVE-2021-20286?

CVE-2021-20286 is a low-severity denial of service vulnerability in Redhat Enterprise Linux, published on 15 Mar 2021. An attacker needs administrator access to exploit it, with no action from the victim.

### Official description

A flaw was found in libnbd 1.7.3. An assertion failure in nbd_unlocked_opt_go in ilb/opt.c may lead to denial of service.

Weakness: CWE-617 (Reachable Assertion)

## Which versions are affected by CVE-2021-20286?

It affects 2 products.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `containerized-data-importer` | SUSE:Linux Enterprise Module for Containers 15 SP2 | All versions | 1.30.0-5.3.2 |
| `kubevirt` | SUSE:Linux Enterprise Module for Containers 15 SP2 | All versions | 0.40.0-5.11.2 |
| `kubevirt` | SUSE:Linux Enterprise Module for Containers 15 SP3 | All versions | 0.40.0-5.11.2 |
| `kubevirt` | openSUSE:Leap 15.3 | All versions | 0.40.0-5.11.2 |
| `libnbd` | openSUSE:Tumbleweed | All versions | 1.9.3-1.2 |

Products: Redhat Enterprise Linux, Redhat Libnbd.

## How do I fix CVE-2021-20286?

Apply the vendor's patch.

## Is CVE-2021-20286 being exploited?

There is no known exploitation of CVE-2021-20286 in the wild and no public exploit code.

## Other vulnerabilities in Redhat Enterprise Linux

- [CVE-2018-14667](https://insights.sbomify.com/CVE-2018-14667/): Red Hat JBoss RichFaces Framework Expression Language Injection (critical 9.8, exploited in the wild)
- [CVE-2021-20325](https://insights.sbomify.com/CVE-2021-20325/): Missing fixes for CVE-2021-40438 and CVE-2021-26691 in the versions of httpd, as shipped in Red Hat Enterprise Linux 8.5.0, causes a securit (critical 9.8)
- [CVE-2018-25011](https://insights.sbomify.com/CVE-2018-25011/): Memory corruption in libwebp (critical 9.8)
- [CVE-2018-25014](https://insights.sbomify.com/CVE-2018-25014/): Other in libwebp (critical 9.8)
- [CVE-2014-3585](https://insights.sbomify.com/CVE-2014-3585/): Supply chain in redhat-upgrade-tool (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-20286 and fix it if it is affected.

What it is: CVE-2021-20286 is a low-severity denial of service vulnerability in Redhat Enterprise Linux, published on 15 Mar 2021. An attacker needs administrator access to exploit it, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-20286 in the wild and no public exploit code.

Affected product: Redhat Enterprise 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-2021-20286/ (Markdown: https://insights.sbomify.com/CVE-2021-20286/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-20286
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-20286
- OSV: https://osv.dev/vulnerability/CVE-2021-20286

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-20286/
Summaries are generated and may contain mistakes; the official description above is the record.