OpenSSL AES-GCM Authentication Bypass in pqc.py

Executive Summary

This vulnerability affects openssl_encrypt versions before 1.4.0. When AES-GCM decryption fails, the system incorrectly falls back to unauthenticated AES-CTR mode in pqc.py. This bypasses integrity verification, allowing attackers to modify ciphertext in transit and perform bit-flipping attacks without detection.

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Detection Guidance

Check if your system uses openssl_encrypt versions before 1.4.0 by running: pip show openssl_encrypt. If installed, inspect pqc.py for AES-CTR fallback logic around lines 1400-1444. Monitor network traffic for failed AES-GCM decryptions triggering fallback to unauthenticated AES-CTR mode.

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Impact Analysis

Attackers could exploit this to tamper with encrypted data during transmission. Since AES-CTR lacks authentication, they can alter ciphertext undetected, potentially decrypting or modifying sensitive information without raising errors. This could lead to data breaches or unauthorized changes to encrypted communications.

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Compliance Impact

This vulnerability likely violates compliance requirements for data integrity and encryption standards in GDPR and HIPAA. Both regulations mandate strong cryptographic protections and integrity verification. The fallback to unauthenticated AES-CTR mode removes these protections, potentially exposing organizations to non-compliance penalties and increased risk of data tampering.

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Mitigation Strategies

Upgrade to openssl_encrypt 1.4.0 or later if available. If not, remove the AES-CTR fallback in pqc.py and ensure GCM authentication failures raise errors instead of falling back. Avoid using affected versions in production until patched.

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