CVE-2025-29779 in PostQuantum-Feldman-VSS
Summary
by MITRE • 03/14/2025
Post-Quantum Secure Feldman's Verifiable Secret Sharing provides a Python implementation of Feldman's Verifiable Secret Sharing (VSS) scheme. In versions 0.7.6b0 and prior, the `secure_redundant_execution` function in feldman_vss.py attempts to mitigate fault injection attacks by executing a function multiple times and comparing results. However, several critical weaknesses exist. Python's execution environment cannot guarantee true isolation between redundant executions, the constant-time comparison implementation in Python is subject to timing variations, the randomized execution order and timing provide insufficient protection against sophisticated fault attacks, and the error handling may leak timing information about partial execution results. These limitations make the protection ineffective against targeted fault injection attacks, especially from attackers with physical access to the hardware. A successful fault injection attack could allow an attacker to bypass the redundancy check mechanisms, extract secret polynomial coefficients during share generation or verification, force the acceptance of invalid shares during verification, and/or manipulate the commitment verification process to accept fraudulent commitments. This undermines the core security guarantees of the Verifiable Secret Sharing scheme. As of time of publication, no patched versions of Post-Quantum Secure Feldman's Verifiable Secret Sharing exist, but other mitigations are available. Long-term remediation requires reimplementing the security-critical functions in a lower-level language like Rust. Short-term mitigations include deploying the software in environments with physical security controls, increasing the redundancy count (from 5 to a higher number) by modifying the source code, adding external verification of cryptographic operations when possible, considering using hardware security modules (HSMs) for key operations.
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Analysis
by VulDB Data Team • 03/14/2025
The Post-Quantum Secure Feldman's Verifiable Secret Sharing library implements a cryptographic scheme designed to protect secret sharing operations against malicious participants who might attempt to manipulate the process. This vulnerability affects versions 0.7.6b0 and earlier, where the secure_redundant_execution function attempts to defend against fault injection attacks by running operations multiple times and comparing results. The fundamental flaw lies in the assumption that Python's execution environment can provide true isolation between redundant executions, which is not guaranteed in practice. This creates a critical weakness that undermines the intended security properties of the system.
The technical implementation suffers from several critical design flaws that render the mitigation ineffective. The constant-time comparison implementation in Python remains vulnerable to timing variations that can be exploited by attackers to infer information about the execution process. Additionally, the randomized execution order and timing mechanisms provide insufficient protection against sophisticated fault injection attacks, particularly when attackers have physical access to the hardware. The error handling mechanisms in the implementation may inadvertently leak timing information about partial execution results, creating additional attack vectors. These weaknesses align with common issues identified in the CWE database under categories related to timing attacks and insufficient randomness.
The operational impact of this vulnerability extends beyond simple information disclosure to potentially allow complete compromise of the secret sharing scheme. Attackers could bypass the redundancy check mechanisms entirely, extract secret polynomial coefficients during share generation or verification processes, force the acceptance of invalid shares during verification, or manipulate the commitment verification process to accept fraudulent commitments. These capabilities represent a complete breakdown of the cryptographic security guarantees that the Verifiable Secret Sharing scheme is designed to provide. The vulnerability affects the core integrity mechanisms that ensure participants cannot manipulate the secret sharing process without detection, making it particularly dangerous in security-critical applications.
The mitigation strategies for this vulnerability must address both immediate and long-term concerns. Short-term solutions include deploying the software in environments with robust physical security controls to prevent attackers from gaining the necessary access for fault injection attacks. Increasing the redundancy count from the default value of 5 to a higher number can provide additional protection, though this approach has diminishing returns. External verification of cryptographic operations when possible offers another layer of defense, while considering hardware security modules for key operations provides stronger protection. The most effective long-term remediation requires reimplementing the security-critical functions in a lower-level language like Rust, which can provide better control over execution timing and memory access patterns. This approach aligns with the ATT&CK framework's recommendations for mitigating timing-based attacks and hardware-level vulnerabilities, particularly in the context of cryptographic implementation security.