CVE-2021-33167 - What Happened, Why It Was Rejected, and a Deeper Look

If you’re searching for clarity on CVE-2021-33167, you’re not alone. Many security enthusiasts and IT professionals stumble upon this CVE code, looking for vulnerability details or an exploit. However, you’ll notice something unusual: this CVE was rejected. In this article, we’ll break down what this means, why it matters, and what you should know about unused or rejected CVEs. We’ll also walk through a real-world scenario for better understanding, including code snippets to illustrate some common CVE reporting mechanics.

What is CVE-2021-33167?

CVE-2021-33167 is an identifier in the Common Vulnerabilities and Exposures (CVE) system. When you look up this number in the National Vulnerability Database (NVD) or on MITRE’s CVE list, you’ll find a message like:

> "This candidate was withdrawn by its CNA. Further investigation showed that this candidate is an unused number."

That’s it! No technical details, no affected product, and definitely no exploit code.

Discovery: Someone discovers or suspects a vulnerability.

2. Reservation: A CNA (CVE Numbering Authority), like a large company or security org, reserves a CVE number.

Is invalid for other technical reasons.

4. Rejection: If no real vulnerability is confirmed, the CVE gets marked “REJECTED”. You’ll often see the note “This is unused”.

For CVE-2021-33167, the number was reserved, but later found unnecessary.

What Happens to a Rejected CVE Number?

Rejected CVEs effectively become dead entries in the CVE system. Researchers searching for “CVE-2021-33167 exploit” will find nothing legitimate. The reserved number helps prevent confusion when cross-referencing between security advisories. No software is affected and there is no patch required.

Sample Workflow: How Does a CVE Get Rejected?

Let’s imagine you’re a security engineer and suspect a vulnerability in open-source software, say a hypothetical Python library.

You contact your CNA or use an automated system to reserve it

{
  "cve_id": "CVE-2021-33167",
  "description": "Buffer Overflow in AwesomeLib v1.2.3",
  "affected_product": "AwesomeLib",
  "version": "1.2.3"
}

Step 2: Realize It’s a False Report

Upon further code review, you find your initial suspicion was incorrect.

# Initial suspicion
def vulnerable_function(data):
    buffer = [] * 10
    for i in range(len(data)):
        buffer[i] = data[i]  # Would fail if data > 10, possible overflow?

# But after checking:
def safe_function(data):
    buffer = [] * 10
    for i in range(min(len(data), 10)):
        buffer[i] = data[i]  # No overflow possible.

You realize the code handles boundaries just fine.

You notify your CNA, who marks the CVE as REJECTED in the database

REJECTED
This candidate was withdrawn by its CNA. Further investigation showed
that this candidate is an unused number.

Real References

- CVE-2021-33167 at MITRE
- CVE-2021-33167 at NVD
- How CVEs Work (MITRE)

What About Exploits?

Since CVE-2021-33167 is unused, there is no exploit. Any website or listing that claims to have a proof-of-concept for this CVE number is misinformed or trying to scam/hijack the attention the CVE number brings.

Why Are Rejected CVEs Publicly Listed?

Transparency is key in security. Listing rejected CVEs helps everyone—vendors, users, security teams—stay on the same page and avoid confusion. It keeps the CVE system honest and prevents “dead numbers” from being reused.

Rejected CVEs help maintain integrity and prevent confusion in the vulnerability ecosystem.

If you stumbled here researching this CVE, now you know: CVE-2021-33167 was simply a placeholder that’s no longer needed.

Timeline

Published on: 02/23/2024 21:15:09 UTC
Last modified on: 02/26/2025 06:26:25 UTC