Overview
In the modern digital landscape, the security of communication channels is of paramount importance. Cryptographic protocols such as mTLS (mutual TLS) are used to ensure the confidentiality and authenticity of these channels. VaulTLS is a widely-used solution for managing mTLS certificates. However, a critical vulnerability coded as CVE-2025-55299 has been discovered in versions of VaulTLS prior to 0.9.1 which can lead to potential system compromise or data leakage. This issue affects a broad range of organizations and individuals using VaulTLS for mTLS certificate management and hence, warrants immediate attention.
Vulnerability Summary
CVE ID: CVE-2025-55299
Severity: Critical (CVSS Score: 9.4)
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: Potential system compromise or data leakage
Affected Products
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Product | Affected Versions
VaulTLS | All versions prior to 0.9.1
How the Exploit Works
The vulnerability arises from the fact that user accounts created through the User web UI in VaulTLS versions prior to 0.9.1 have an empty but not NULL password set. This allows attackers to log in using an empty password. The situation is further exacerbated by the fact that disabling the password-based login only affected the frontend, leaving the API accessible. An attacker can leverage this oversight to log in via the API, potentially compromising the system or causing data leakage.
Conceptual Example Code
The following conceptual example demonstrates how an attacker might exploit this vulnerability. Please note that this is a simulated representation and not actual exploit code:
POST /api/login HTTP/1.1
Host: target.example.com
Content-Type: application/json
{ "username": "victim_username", "password": "" }In the above example, an attacker sends a POST request to the /api/login endpoint with a legitimate username and an empty password. If the system is vulnerable, it will authenticate the request and grant the attacker access.
Mitigation Guidance
Users of VaulTLS are advised to immediately upgrade to version 0.9.1 or later where this vulnerability has been fixed. In cases where immediate upgrade is not feasible, employing a Web Application Firewall (WAF) or Intrusion Detection System (IDS) can serve as a temporary mitigation measure. This can help detect and prevent unauthorized login attempts. However, this should be considered a stop-gap measure and not a permanent solution. The only definitive mitigation is to upgrade the affected software to a version where this vulnerability has been patched.