CVE-2025-52556 in rfc3161-client
Summary
by MITRE • 06/21/2025
rfc3161-client is a Python library implementing the Time-Stamp Protocol (TSP) described in RFC 3161. Prior to version 1.0.3, there is a flaw in the timestamp response signature verification logic. In particular, chain verification is performed against the TSR's embedded certificates up to the trusted root(s), but fails to verify the TSR's own signature against the timestamping leaf certificates. Consequently, vulnerable versions perform insufficient signature validation to properly consider a TSR verified, as the attacker can introduce any TSR signature so long as the embedded leaf chains up to some root TSA. This issue has been patched in version 1.0.3. There is no workaround for this issue.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 06/21/2025
The vulnerability identified as CVE-2025-52556 affects the rfc3161-client Python library, which implements the Time-Stamp Protocol (TSP) as defined in RFC 3161. This protocol serves a critical role in digital timestamping operations, providing cryptographic proof of when a document or data was created or modified. The flaw exists in versions prior to 1.0.3 and fundamentally undermines the security guarantees that timestamp responses should provide. The vulnerability represents a significant weakness in the certificate chain verification process that is essential for maintaining trust in timestamping operations.
The technical flaw manifests in the signature verification logic where the library performs chain verification against the Timestamp Response's embedded certificates but fails to validate the Timestamp Response's own signature against the timestamping leaf certificates. This creates a critical gap in validation where the system accepts any valid certificate chain from the embedded certificates up to a trusted root without ensuring that the actual timestamp response signature matches the expected signature from the leaf certificate. The vulnerability specifically relates to CWE-330 Use of Insufficiently Random Values, as it allows an attacker to potentially bypass proper signature validation mechanisms. This issue directly impacts the integrity verification process that is fundamental to timestamping security.
The operational impact of this vulnerability is severe as it allows attackers to forge timestamp responses that appear valid to vulnerable systems. An attacker can construct a malicious timestamp response with any signature so long as the embedded certificate chain leads to a trusted root certificate authority. This effectively undermines the entire timestamping infrastructure by enabling the creation of false timestamps that would be accepted as legitimate by systems using vulnerable versions of the library. The vulnerability affects any system relying on timestamp validation for security purposes, including code signing verification, document integrity checks, and cryptographic timestamping operations. This weakness can be exploited in various attack scenarios including software supply chain attacks where forged timestamps could be used to bypass security controls.
The security implications extend beyond simple signature validation failure as this vulnerability directly contradicts the core principles of certificate-based authentication and timestamp integrity. According to ATT&CK framework, this vulnerability could be leveraged under technique T1553.004 for bypassing signature validation controls. The patch in version 1.0.3 addresses this by implementing proper signature verification that ensures the timestamp response signature matches the expected signature from the timestamping leaf certificates. Organizations should immediately upgrade to version 1.0.3 or later to remediate this vulnerability, as no workaround exists for this particular flaw. The vulnerability highlights the importance of comprehensive signature validation in cryptographic libraries and demonstrates how seemingly minor implementation gaps can create significant security risks in timestamping and certificate validation systems.