When you explore the world of cybersecurity, you often come across headlines about dangerous vulnerabilities and critical exploits. However, not every CVE (Common Vulnerabilities and Exposures) entry tells the same story. In this post, we’re going to look at CVE-2021-33136, a vulnerability you may have seen referenced in databases and lists, but for a different reason — it was rejected because it is unused.

CVE-2021-33136 is a unique entry in the CVE database.

- According to the official CVE entry, this CVE was rejected.

Reason for rejection (from the listing): “This is unused.”

That’s right — no exploit, no patch, no software affected, and no code, simply because this CVE was reserved but never put to use.

Why Do Unused or Rejected CVEs Exist?

Sometimes, CVE numbers are assigned in advance, especially for large-scale projects or vulnerability bounty programs. These placeholders allow coordination between vendors, researchers, and response teams before anything is announced publicly.

Here’s a rough description of how it happens

Step 1: Reporter thinks they've found a vulnerability.
Step 2: Reporter requests a CVE ID for tracking.
Step 3: Further investigation shows no real bug or duplicate issue.
Step 4: CVE board marks the CVE as rejected, with info such as:
    "REJECTED - This is unused."

So, CVE-2021-33136 falls into this very category. No vulnerability, no exposure, just a placeholder that never got used.

If you’re looking for code, here’s what you’ll find for CVE-2021-33136

# Sadly, there is no vulnerable code for CVE-2021-33136.
# The entry was rejected before any details were published.

def cve_exploit():
    raise Exception("CVE-2021-33136 does not exist.")

try:
    cve_exploit()
except Exception as e:
    print(e)
# Output: CVE-2021-33136 does not exist.

Diligence: Vulnerabilities aren’t published without verification, reducing false alarms.

3. Record keeping: There’s value in knowing what wasn’t a hazard, to avoid confusion in audits or future checks.

References

- Original MITRE CVE Entry for CVE-2021-33136
- CVE List Main Page
- Why CVE IDs can be rejected (see “What does ‘REJECTED’ mean for a CVE ID?”)

TL;DR

CVE-2021-33136 is a “non-vulnerability.” It was assigned, checked, and then rejected because nothing was discovered or disclosed needing urgent action. In cybersecurity, knowing what isn’t a threat is almost as important as knowing what is. So, if you ever see this CVE cited anywhere, now you know the exclusive truth — it simply doesn’t exist.


> Stay skeptical, double-check every CVE — not all numbers mean there’s something to fix!

Timeline

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