EUVD-2025-3602

Comprehensive Technical Analysis of EUVD-2025-3602

1. Vulnerability Assessment and Severity Evaluation

Vulnerability Description: The vulnerability affects the PAM-PKCS#11 module, a Linux-PAM login module that facilitates X.509 certificate-based user login. Prior to version 0.6.13, the module does not require a signature with the private key when cert_policy is set to none (the default value). This allows an attacker to create a token using the user's public data and a known PIN, enabling unauthorized login.

Severity Evaluation: The vulnerability has a base score of 9.2 according to CVSS 4.0, indicating a critical severity. The vector string CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:L/SC:L/SI:L/SA:L highlights the following:

• Attack Vector (AV): Network (N)
• Attack Complexity (AC): Low (L)
• Authentication (AT): Physical (P)
• Privileges Required (PR): None (N)
• User Interaction (UI): None (N)
• Confidentiality Impact (VC): High (H)
• Integrity Impact (VI): High (H)
• Availability Impact (VA): Low (L)
• Scope Change (SC): Low (L)
• Scope Impact (SI): Low (L)
• Scope Availability (SA): Low (L)

This indicates that the vulnerability can be exploited remotely with low complexity, requiring no user interaction or privileges, and can result in high confidentiality and integrity impacts.

2. Potential Attack Vectors and Exploitation Methods

Attack Vectors:

• Network-Based Attacks: An attacker can exploit this vulnerability over the network by creating a token with the user's public data and a known PIN.
• Physical Access: Physical access to the system can also be leveraged to exploit this vulnerability, especially in scenarios where the attacker can manipulate the token directly.

Exploitation Methods:

• Token Creation: An attacker can create a token using the user's public certificate and a PIN known to the attacker.
• Unauthorized Login: The attacker can then use this token to log in as the user without requiring a signature with the private key.

3. Affected Systems and Software Versions

Affected Systems:

• Linux systems using the PAM-PKCS#11 module for X.509 certificate-based login.

Affected Software Versions:

• All versions of pam_pkcs11 prior to 0.6.13.

4. Recommended Mitigation Strategies

Immediate Mitigation:

• Configuration Change: Set cert_policy = signature; in the pam_pkcs11.conf file to enforce signature checks with the private key.

Long-Term Mitigation:

• Software Update: Upgrade to pam_pkcs11 version 0.6.13 or later, which includes the fix for this vulnerability.
• Regular Audits: Conduct regular security audits to ensure that all configurations are secure and up-to-date.
• Monitoring: Implement monitoring to detect any unauthorized login attempts or suspicious activities.

5. Impact on European Cybersecurity Landscape

Impact Analysis:

• Widespread Use: The PAM-PKCS#11 module is widely used in various Linux-based systems, making this vulnerability a significant risk for organizations relying on X.509 certificate-based authentication.
• Critical Infrastructure: This vulnerability could impact critical infrastructure, including government agencies, financial institutions, and healthcare providers, which often use certificate-based authentication for secure access.
• Compliance: Organizations must ensure compliance with European cybersecurity regulations, such as GDPR and NIS Directive, by addressing this vulnerability promptly.

6. Technical Details for Security Professionals

Technical Overview:

• Module Functionality: The PAM-PKCS#11 module allows users to authenticate using X.509 certificates stored on smart cards or other PKCS#11 tokens.
• Vulnerability Root Cause: The default configuration (cert_policy = none) does not enforce a signature check with the private key, allowing an attacker to bypass authentication.
• Fix Implementation: The fix involves changing the default behavior to require a signature check, ensuring that only legitimate tokens can be used for authentication.

References:

• GitHub Advisory: GHSA-8r8p-7mgp-vf56
• Relevant Commits:
  • Commit 470263258d1ac59c5eade439c4d9caba0097e6e6
  • Commit b665b287ff955bbbd9539252ff9f9e2754c3fb48
  • Commit d9530167966a77115db6e885d459382a2e52ee9e
• Release Notes: pam_pkcs11-0.6.13

Conclusion: This vulnerability underscores the importance of robust authentication mechanisms and regular updates to security configurations. Organizations should prioritize updating to the latest version of pam_pkcs11 and implementing the recommended mitigation strategies to protect against potential exploitation.