DavidOsipov PostQuantum-Feldman-VSS up to 0.7.6b0 information exposure

Summaryinfo

A vulnerability classified as problematic has been found in DavidOsipov PostQuantum-Feldman-VSS up to 0.7.6b0. This vulnerability affects unknown code. The manipulation leads to information exposure. This vulnerability is listed as CVE-2025-29780. The attack must be carried out locally. There is no available exploit.

Detailsinfo

A vulnerability was found in DavidOsipov PostQuantum-Feldman-VSS up to 0.7.6b0. It has been rated as problematic. This issue affects some unknown processing. The manipulation with an unknown input leads to a information exposure vulnerability. Using CWE to declare the problem leads to CWE-203. The product behaves differently or sends different responses under different circumstances in a way that is observable to an unauthorized actor, which exposes security-relevant information about the state of the product, such as whether a particular operation was successful or not. Impacted is confidentiality. The summary by CVE is:

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 `feldman_vss` library contains timing side-channel vulnerabilities in its matrix operations, specifically within the `_find_secure_pivot` function and potentially other parts of `_secure_matrix_solve`. These vulnerabilities are due to Python's execution model, which does not guarantee constant-time execution. An attacker with the ability to measure the execution time of these functions (e.g., through repeated calls with carefully crafted inputs) could potentially recover secret information used in the Verifiable Secret Sharing (VSS) scheme. The `_find_secure_pivot` function, used during Gaussian elimination in `_secure_matrix_solve`, attempts to find a non-zero pivot element. However, the conditional statement `if matrix[row][col] != 0 and row_random < min_value:` has execution time that depends on the value of `matrix[row][col]`. This timing difference can be exploited by an attacker. The `constant_time_compare` function in this file also does not provide a constant-time guarantee. The Python implementation of matrix operations in the _find_secure_pivot and _secure_matrix_solve functions cannot guarantee constant-time execution, potentially leaking information about secret polynomial coefficients. An attacker with the ability to make precise timing measurements of these operations could potentially extract secret information through statistical analysis of execution times, though practical exploitation would require significant expertise and controlled execution environments. Successful exploitation of these timing side-channels could allow an attacker to recover secret keys or other sensitive information protected by the VSS scheme. This could lead to a complete compromise of the shared secret. As of time of publication, no patched versions of Post-Quantum Secure Feldman's Verifiable Secret Sharing exist, but other mitigations are available. As acknowledged in the library's documentation, these vulnerabilities cannot be adequately addressed in pure Python. In the short term, consider using this library only in environments where timing measurements by attackers are infeasible. In the medium term, implement your own wrappers around critical operations using constant-time libraries in languages like Rust, Go, or C. In the long term, wait for the planned Rust implementation mentioned in the library documentation that will properly address these issues.

The advisory is shared at github.com. The identification of this vulnerability is CVE-2025-29780 since 03/11/2025. The exploitation is known to be difficult. An attack has to be approached locally. Neither technical details nor an exploit are publicly available. MITRE ATT&CK project uses the attack technique T1592 for this issue.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Vendor

• DavidOsipov

Name

• PostQuantum-Feldman-VSS

Version

• 0.7.6b0

Website

• Product: https://github.com/DavidOsipov/PostQuantum-Feldman-VSS/

CPE 2.3info

• 🔍

CPE 2.2info

• 🔍

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Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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