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Most posts about CVEs (Common Vulnerabilities and Exposures) talk about critical security loopholes and how hackers could use them. But not all CVEs are about real threats. Sometimes, an entry is made, then dropped because it turned out to be wrong, not a security risk, or just unused by researchers. That’s the story behind CVE-2021-33156. In this long-read, we’ll break down what happens when a CVE gets rejected, why this happens, and what you should know about this unused entry. (Spoiler: There’s no exploit or vulnerability here, but there’s still much to learn!)

What Is CVE-2021-33156?

If you check the official CVE List entry for CVE-2021-33156, you’ll see a very short message:

 REJECT    
Reason: This candidate was withdrawn by its requester.   
Notes: None

In security language, REJECT means the entry is not valid anymore. CVEs like this one are actually common. If you dive deeper, you’ll find that the reason for the rejection here is:
> This is unused.

That means there’s no real vulnerability, no danger, and nothing to patch. But why does that happen?

Review: The issue is checked by more people (often vendors or researchers).

4. Correction or Withdrawal: Sometimes, it’s found that the bug is not real, or it’s already covered by another CVE, or it just doesn’t exist.
5. REJECT: If there’s no problem, the CVE is marked as “rejected” and removed from lists of live vulnerabilities.

Here’s what a rejected/unassigned CVE entry might look like in JSON format for your security tools

{
  "cve": "CVE-2021-33156",
  "status": "REJECTED",
  "reason": "This is unused.",
  "notes": "None"
}

And for your vulnerability management scripts, it’s safe to add logic that ignores rejected CVEs. For example, in Python:

if cve_entry['status'] == 'REJECTED':
    print(f"{cve_entry['cve']} is not an active vulnerability. Skipping.")

Why Is It Useful To Keep Rejected CVEs Around?

You might wonder—for something with no risk, why not just delete it? The answer is tracking. Here’s why rejected CVEs are valuable:

Audit Public History: Security teams can see that the potential risk was reviewed.

- Prevents Confusion: If someone finds an old blog or scan mentioning CVE-2021-33156, they can verify it’s not a concern.

What Should Security Teams Do About Rejected CVEs?

If you see CVE-2021-33156 in vulnerability scan results, you can safely ignore it. Update your dashboards or reports to reflect the “REJECTED” status. Here’s a sample filter in a report query:

SELECT * FROM vulnerabilities
WHERE cve_status != 'REJECTED'

This makes sure you only see active, real threats.

Useful References

- Official CVE-2021-33156 Entry
- MITRE: How to Interpret CVE Entries
- NIST NVD: CVE-2021-33156

If you see it in reports, mark it as safe.

Sometimes staying secure means knowing what not to worry about. Next time you spot a rejected CVE like CVE-2021-33156, you’ll know exactly what it means. Stay informed, stay secure!


*Written for defenders, by defenders. Share and stay updated on what really matters in vulnerability management.*

Timeline

Published on: 02/23/2024 21:15:09 UTC
Last modified on: 02/26/2025 06:26:24 UTC