CVE-2023-3252 is an arbitrary file write vulnerability found in certain logging components, allowing an authenticated, remote attacker with administrator rights to overwrite any file on the system with log data. This issue arises from inadequate checks when configuring log file destinations, letting attackers redirect logs to critical system files. With this access, attackers can cause major service disruptions, even bringing down the entire system through a Denial of Service (DoS).

In this article, we'll explain how CVE-2023-3252 works, see practical exploitation details, review sample code, and share references for deeper reading.

What Is CVE-2023-3252?

The vulnerability stems from how certain software allows privileged users to set or change the destination for log output. If the software doesn’t restrict paths or filenames for the logs, attackers with enough privileges can tell the software to write logs into important files. This overwrites the content of those files with log data.

Affected systems could experience total failure if key configuration files or executables are overwritten.

* CWE Reference: CWE-123: Write-what-where Condition
* CVE Details page: CVE-2023-3252

Here’s a simplified step-by-step of how an attacker leverages CVE-2023-3252

1. Login as Admin: The attacker logs in using valid administrator credentials (maybe from phishing or insider threat).
2. Change Log File Path: Using administrative controls, the attacker changes the log file location to point to a sensitive file (like /etc/passwd on Linux).
3. Trigger Logging: The attacker performs actions that generate log entries. Every new log entry overwrites or appends to the chosen file.

Consequences: Critical system files get corrupted, leading to malfunction or crash.

Because overwriting files like /etc/passwd or app configuration files can break system authentication or make programs unreadable by the system, this vector is enough to DoS the host. It could also be used for local privilege escalation or even arbitrary code execution in certain circumstances.

Below is a (simplified) Python-like snippet showing how this issue might look in code

class Logger:
    def __init__(self):
        self.log_path = "/var/log/app.log"

    def set_log_file(self, new_path):
        # Vulnerable: no check on new_path
        self.log_path = new_path

    def log(self, message):
        with open(self.log_path, "a") as logfile:
            logfile.write(message + "\n")

# Admin user changes the log path to /etc/passwd
logger = Logger()
logger.set_log_file("/etc/passwd")

# Every log will now go into /etc/passwd, corrupting it
logger.log("This is a malicious log message.")

What's wrong:
Notice there’s no validation for new_path in set_log_file(). The attacker can change the destination to *any* file!

Real-World Exploitation Example

Let’s say an attacker with admin access changes the log destination to /etc/shadow, /etc/hosts, or even web server config files. Then, by triggering logs (or flooding with log activity), these files get filled with log data. On system restart or next access, those services crash or stop working, resulting in denial of service.

* Step 1: Log in to the web management interface as admin.
* Step 2: Navigate to settings to update the log file location.
* Step 3: Change destination from /var/log/app.log to /etc/passwd.
* Step 4: Perform actions that generate logs (e.g., failed logins, invalid requests).
* Step 5: System users now cannot authenticate or the host fails to boot.

Mitigations

- Input Validation: Restrict log file destinations to specific directories, e.g., only /var/log.

- Least Privilege: Only allow system administrators to configure log destinations, but always restrict the scope.

Example fix (Python)

import os

def set_log_file(self, new_path):
    allowed_dir = "/var/log/myapp/"
    # Only allow files in allowed_dir
    if os.path.commonprefix([os.path.abspath(new_path), allowed_dir]) == allowed_dir:
        self.log_path = new_path
    else:
        raise Exception("Invalid log file location.")

References & Further Reading

- CVE-2023-3252 - NVD
- CWE-123: Write-what-where Condition
- Common Logging Security Issues by OWASP
- Syslog Security - RedHat Docs

Summary

CVE-2023-3252 is a serious, real-world vulnerability caused by failing to validate log file paths. When exploited, it turns application logging into a powerful weapon for denial of service, and with enough creativity, potentially more. Always validate and restrict where your code writes files, especially when privileged users can change those settings!

Timeline

Published on: 08/29/2023 19:15:00 UTC
Last modified on: 09/01/2023 14:34:00 UTC