# CVE-2021-28484: Infinite loop in Yubico yubihsm-connector

> An attacker can cause a denial of service in the YubiHSM connector by sending malformed requests, requiring a restart to recover.

- **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:** 14 Apr 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-8m9g-647g-5pxw

## What is CVE-2021-28484?

CVE-2021-28484 is a high-severity denial of service vulnerability in Fedoraproject Fedora, published on 14 Apr 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

An issue was discovered in the /api/connector endpoint handler in Yubico yubihsm-connector before 3.0.1 (in YubiHSM SDK before 2021.04). The handler did not validate the length of the request, which can lead to a state where yubihsm-connector becomes stuck in a loop waiting for the YubiHSM to send it data, preventing any further operations until the yubihsm-connector is restarted. An attacker can send 0, 1, or 2 bytes to trigger this.

Weakness: CWE-835 (Loop with Unreachable Exit Condition)

## Which versions are affected by CVE-2021-28484?

2 open source packages ship an affected version, including github.com/Yubico/yubihsm-connector. It affects 2 products.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/Yubico/yubihsm-connector` | Go | All versions | 3.0.1 |
| `github.com/Yubico/yubihsm-connector` | Go | All versions | 3.0.1 |

Products: Fedoraproject Fedora, Yubico Yubihsm Connector.

## How do I fix CVE-2021-28484?

Upgrade github.com/Yubico/yubihsm-connector to 3.0.1 or later.

## Is CVE-2021-28484 being exploited?

There is no known exploitation of CVE-2021-28484 in the wild and no public exploit code.

## Other vulnerabilities in Fedoraproject Fedora

- [CVE-2024-4577](https://insights.sbomify.com/CVE-2024-4577/): PHP-CGI OS Command Injection (critical 9.8, exploited in the wild)
- [CVE-2021-39226](https://insights.sbomify.com/CVE-2021-39226/): Grafana Authentication Bypass (critical 9.8, exploited in the wild)
- [CVE-2019-5544](https://insights.sbomify.com/CVE-2019-5544/): VMware ESXi and Horizon DaaS OpenSLP Heap-Based Buffer Overflow (critical 9.8, exploited in the wild)
- [CVE-2024-4947](https://insights.sbomify.com/CVE-2024-4947/): Google Chromium V8 Type Confusion (critical 9.6, exploited in the wild)
- [CVE-2024-4671](https://insights.sbomify.com/CVE-2024-4671/): Google Chromium Visuals Use-After-Free (critical 9.6, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-28484 and fix it if it is affected.

What it is: CVE-2021-28484 is a high-severity denial of service vulnerability in Fedoraproject Fedora, published on 14 Apr 2021. 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-2021-28484 in the wild and no public exploit code.

Affected packages and fixed versions:
- github.com/Yubico/yubihsm-connector (Go): affected all versions; fixed in 3.0.1
- github.com/Yubico/yubihsm-connector (Go): affected all versions; fixed in 3.0.1

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-2021-28484/ (Markdown: https://insights.sbomify.com/CVE-2021-28484/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-28484
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-28484
- OSV: https://osv.dev/vulnerability/CVE-2021-28484

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-28484/
Summaries are generated and may contain mistakes; the official description above is the record.