EUVD-2025-18387

Comprehensive Technical Analysis of EUVD-2025-18387

1. Vulnerability Assessment and Severity Evaluation

Vulnerability Description: The Mojolicious::Plugin::CaptchaPNG version 1.05 for Perl uses a weak random number source for generating CAPTCHA text and image noise. Specifically, it relies on the built-in rand() function, which is not cryptographically secure.

Severity Evaluation: The vulnerability has a base score of 9.1 according to CVSS 3.1, indicating a critical severity level. The vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N breaks down as follows:

• Attack Vector (AV): Network (N)
• Attack Complexity (AC): Low (L)
• Privileges Required (PR): None (N)
• User Interaction (UI): None (N)
• Scope (S): Unchanged (U)
• Confidentiality (C): High (H)
• Integrity (I): High (H)
• Availability (A): None (N)

This high severity is due to the potential for significant confidentiality and integrity impacts without requiring any special privileges or user interaction.

2. Potential Attack Vectors and Exploitation Methods

Attack Vectors:

• Brute Force Attacks: An attacker could predict the CAPTCHA text due to the weak randomness, allowing automated systems to bypass the CAPTCHA.
• Replay Attacks: If the randomness is predictable, an attacker could reuse previously generated CAPTCHA solutions.
• Data Leakage: Predictable CAPTCHA text could be used to infer sensitive information or patterns in the application's logic.

Exploitation Methods:

• Automated Scripts: Attackers could write scripts to predict and solve CAPTCHAs, enabling automated account creation, spamming, or other malicious activities.
• Man-in-the-Middle (MitM): An attacker intercepting network traffic could more easily predict and solve CAPTCHAs, facilitating unauthorized access.

3. Affected Systems and Software Versions

Affected Software:

• Mojolicious::Plugin::CaptchaPNG version 1.05

Affected Systems:

• Any system or application using the Mojolicious::Plugin::CaptchaPNG version 1.05 for CAPTCHA generation.

4. Recommended Mitigation Strategies

Immediate Mitigation:

• Upgrade: Upgrade to Mojolicious::Plugin::CaptchaPNG version 1.06 or later, which addresses the vulnerability by using a more secure random number generator.
• Patch: Apply any available patches from the vendor that fix the random number generation issue.

Long-Term Mitigation:

• Cryptographic Randomness: Ensure that all security-sensitive operations use cryptographically secure random number generators.
• Regular Audits: Conduct regular security audits of all third-party libraries and plugins to identify and mitigate similar vulnerabilities.
• Monitoring: Implement monitoring to detect unusual patterns in CAPTCHA solving, which could indicate automated attacks.

5. Impact on European Cybersecurity Landscape

Regulatory Compliance:

• Organizations using the affected software may be in violation of GDPR and other data protection regulations if the vulnerability leads to data breaches.
• Compliance with EU cybersecurity directives such as NIS2 may require immediate remediation of such vulnerabilities.

Operational Impact:

• Compromised CAPTCHAs could lead to increased spam, fraud, and unauthorized access, affecting the integrity and availability of services.
• Public trust in online services could be eroded if users perceive that security measures are inadequate.

6. Technical Details for Security Professionals

Vulnerability Details:

• The rand() function in Perl is not suitable for security-sensitive operations due to its predictable nature.
• The vulnerability arises from the use of rand() to generate both the CAPTCHA text and the image noise, making it easier for attackers to predict the output.

References:

• NVD Entry: CVE-2025-40916
• Perl rand() Documentation: perlfunc#rand
• Vulnerable Code Diff: Mojolicious-Plugin-CaptchaPNG-1.05
• Fixed Version Changes: Mojolicious-Plugin-CaptchaPNG-1.06
• Secure Random Data Guide: Random Data for Security

Assigner:

• CPANSec

EPSS:

• Not Available (N/A)

ENISA IDs:

• Product: [{"id":"f7aa8d59-9f0d-3467-a89a-33aaa9247646","product":{"name":"Mojolicious::Plugin::CaptchaPNG"},"product_version":"1.05"}]
• Vendor: [{"id":"d70bb401-1676-3b4a-a4d7-57bee1563cb7","vendor":{"name":"GRYPHON"}}]

By addressing this vulnerability promptly, organizations can significantly reduce the risk of automated attacks and ensure the integrity of their CAPTCHA-based security measures.