CVE-2021-37405 stands out in security databases—but not because it’s dangerous. Rather, it’s become a point of curiosity in cybersecurity circles because of its rejected status and its reason: “This is unused”. In this post, we’ll break down what this means, how CVE assignments work, and what you should know as a researcher or user. We'll also look at how to avoid confusion around rejected CVEs.

What is CVE-2021-37405?

A Common Vulnerabilities and Exposures (CVE) number helps IT professionals and researchers track security issues in software and hardware. Each CVE should refer to a real, unique vulnerability.

Original Reference

CVE-2021-37405 appears in the official MITRE CVE database with a clear rejection message:

> "REJECTED
> Reason: This candidate was withdrawn by its submitter.
> Notes: None.
> This is unused."

There is a clerical error.

Once discovered, MITRE or another authority can mark the CVE as REJECTED. This is essentially a way to maintain the integrity of the database and avoid confusion.

The Actual Reason

For CVE-2021-37405, the key line is:

“This is unused.”

No vulnerability was ever associated with this CVE. It was issued in error or withdrawn by whoever asked for it. It’s a placeholder with no real-world exploit, patch, or risk to systems.

A real CVE post might include a code snippet showing how to exploit a vulnerability. For example

# Simulated Exploit Template for a Real Vulnerability

import requests

target = "http://vulnerable-site.com/login";
payload = {"username": "' OR 1=1--", "password": "irrelevant"}

r = requests.post(target, data=payload)
if "Welcome" in r.text:
    print("Possible SQLi Exploit!")

But for CVE-2021-37405

There’s no code, configuration, or tool to use. No vulnerability exists.

What Should You Do if You See This CVE?

If you see CVE-2021-37405 in a vulnerability scan or a vendor advisory, you can safely ignore it. There is nothing to patch, fix, or monitor related to this entry.

Best Practices

- Double-check sources: Always verify the current status of a CVE in the MITRE CVE list.

Don’t panic: If a CVE is REJECTED with “unused,” it’s likely a database artifact.

- Focus on real risks: Pay attention to CVEs with valid descriptions, affected software, and actual exploit details.

Why Do Rejected CVEs Matter?

They help keep the global CVE system clean, transparent, and accurate. Even unused entries remain in the database so researchers never waste time on ghost vulnerabilities.

Final Thoughts

CVE-2021-37405 demonstrates the self-correcting nature of global security databases. While you may not find a juicy bug or clever exploit here, its mere existence shows commitment to clarity and accountability in cybersecurity.

If you ever come across another rejected CVE with “This is unused”, you now know: there’s nothing lurking under the hood.

References

- MITRE CVE-2021-37405 Entry
- MITRE: Understanding CVEs
- NVD Entry for CVE-2021-37405


Stay informed, but let this one go. There’s no story here—except for its own nearly invisible footnote in cybersecurity history!

Timeline

Published on: 02/23/2024 21:15:10 UTC
Last modified on: 09/04/2025 00:43:38 UTC