EUVD-2025-38333

Comprehensive Technical Analysis of EUVD-2025-38333

1. Vulnerability Assessment and Severity Evaluation

Vulnerability Description: The vulnerability in calibre, an e-book manager, affects versions 8.13.0 and prior. The issue arises from the lack of validation for filenames when handling binary assets in FB2 (FictionBook) files. This allows an attacker to write arbitrary files on the filesystem when a user views or converts a malicious FB2 file, potentially leading to arbitrary code execution.

Severity Evaluation: The Base Score of 9.3 (CVSS:4.0) indicates a critical vulnerability. The vector string CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H breaks down as follows:

• Attack Vector (AV): Local (L) - The attacker must have local access to exploit the vulnerability.
• Attack Complexity (AC): Low (L) - The attack is relatively straightforward to execute.
• Authentication (AT): None (N) - No authentication is required.
• Privileges Required (PR): None (N) - No special privileges are needed.
• User Interaction (UI): Physical (P) - The attacker must physically interact with the system.
• Confidentiality (VC), Integrity (VI), Availability (VA): High (H) - The vulnerability significantly impacts confidentiality, integrity, and availability.
• Scope Change (SC), Scope Integrity (SI), Scope Availability (SA): High (H) - The vulnerability can affect resources beyond its security scope.

2. Potential Attack Vectors and Exploitation Methods

Attack Vectors:

• Malicious FB2 Files: An attacker can craft a malicious FB2 file with specially designed filenames that exploit the vulnerability.
• Social Engineering: Attackers may use phishing or other social engineering techniques to trick users into opening the malicious FB2 file.

Exploitation Methods:

• Arbitrary File Write: By exploiting the lack of filename validation, an attacker can write arbitrary files to the filesystem.
• Code Execution: The attacker can leverage the arbitrary file write to place malicious code in executable paths, leading to arbitrary code execution.

3. Affected Systems and Software Versions

Affected Software:

• Calibre: Versions 8.13.0 and prior.

Affected Systems:

• Any system running the affected versions of calibre, including personal computers, servers, and any device used for e-book management.

4. Recommended Mitigation Strategies

Immediate Actions:

• Update Software: Upgrade to calibre version 8.14.0 or later, which includes the fix for this vulnerability.
• User Awareness: Educate users about the risks of opening files from untrusted sources.

Long-Term Strategies:

• Input Validation: Implement robust input validation mechanisms to ensure filenames and other inputs are properly sanitized.
• Regular Audits: Conduct regular security audits and code reviews to identify and mitigate similar vulnerabilities.

5. Impact on European Cybersecurity Landscape

Potential Impact:

• Widespread Use: Calibre is widely used for e-book management, making this vulnerability a significant risk for a broad user base.
• Critical Infrastructure: If used in critical infrastructure or sensitive environments, the vulnerability could have severe consequences.
• Data Integrity: The ability to write arbitrary files can compromise data integrity and confidentiality, leading to potential data breaches.

Regulatory Compliance:

• GDPR: Organizations must ensure they comply with GDPR regulations, especially regarding data protection and breach reporting.
• NIS Directive: Critical infrastructure operators must adhere to the Network and Information Systems (NIS) Directive, ensuring robust cybersecurity measures are in place.

6. Technical Details for Security Professionals

Technical Analysis:

• Root Cause: The vulnerability stems from a lack of filename validation when handling binary assets in FB2 files.
• Exploit Mechanism: The attacker can craft an FB2 file with malicious filenames that, when processed by calibre, write arbitrary files to the filesystem.
• Mitigation: The fix in version 8.14.0 involves implementing proper filename validation to prevent arbitrary file writes.

References:

• GitHub Advisory: GHSA-hpwq-c98h-xp8g
• Commit Reference: 6f94bce214bf7d43c829804db3741afa5e83c0c5

Conclusion: This vulnerability in calibre underscores the importance of robust input validation and regular software updates. Organizations and individuals using calibre should prioritize updating to the latest version to mitigate the risk of exploitation. The European cybersecurity landscape must remain vigilant against such vulnerabilities to protect data integrity and ensure compliance with regulatory standards.