Overview
In this blog post, we are going to discuss an important security vulnerability that affects Finit, a fast init system for Linux. This vulnerability, identified as CVE-2025-29906, allows an attacker to bypass authentication protocols through the `tty` configuration directive, potentially granting them unauthorized access to a system. Such a vulnerability is particularly dangerous as it opens up a system to potential compromise and data leakage.
Vulnerability Summary
CVE ID: CVE-2025-29906
Severity: High (8.6 CVSS)
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: Potential system compromise or data leakage
Affected Products
No phone number, email, or personal info required.
Product | Affected Versions
Finit | 3.0-rc1 to 4.10
How the Exploit Works
In versions of Finit ranging from 3.0-rc1 and prior to 4.11, an implementation of getty for the `tty` configuration directive is bundled which can bypass the `/bin/login`. This means that an attacker can log in as any user without needing to authenticate. Once the attacker gains unauthorized access, they can potentially compromise the system or exfiltrate sensitive data.
Conceptual Example Code
Here’s a conceptual example of how the vulnerability might be exploited. In this example, we’re illustrating how an attacker might bypass authentication and log in as a superuser:
$ tty
/dev/tty1
$ finit/tty getty
login: root
password: <no password entered>
# User is logged in as root without entering a passwordImpact of the Vulnerability
Given the high CVSS score, the potential impact of this vulnerability is significant. A successful exploit could lead to unauthorized system access, potential system compromise, or data leakage. Depending on the permissions of the user the attacker logs in as, they could potentially have full control over the system.
How to Mitigate the Vulnerability
The vulnerability has been patched in Finit version 4.11. As such, the best way to mitigate this vulnerability is to update Finit to that version or newer. If updating is not immediately possible, using a Web Application Firewall (WAF) or Intrusion Detection System (IDS) can provide temporary mitigation by detecting and blocking attempts to exploit the vulnerability.