CVE-2007-2640 in LibTMCG
Summary
by MITRE
LibTMCG before 1.1.1 does not perform a range check to avoid "trivial group generators," which allows attackers to obtain sensitive information about private cards.
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Analysis
by VulDB Data Team • 08/31/2018
The vulnerability identified as CVE-2007-2640 affects LibTMCG versions prior to 1.1.1 and represents a significant cryptographic weakness that undermines the security of card-based authentication systems. This issue stems from the library's failure to implement proper range checking mechanisms when generating group generators, creating opportunities for attackers to exploit mathematical properties of the cryptographic implementation. The vulnerability specifically targets the generation of trivial group generators that should be excluded from the cryptographic process to maintain security integrity.
The technical flaw manifests in the cryptographic algorithm's generation of group parameters where certain values are mathematically trivial and predictable, allowing attackers to perform targeted attacks against the system. When these trivial generators are used in the cryptographic protocol, they can reveal information about the underlying private keys or card data through mathematical relationships that are normally obscured by proper parameter selection. This weakness is particularly dangerous in card-based authentication systems where the private card information must remain protected against unauthorized access.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can enable attackers to reconstruct private card data and potentially impersonate legitimate users within the system. The lack of range checking creates a backdoor that allows adversaries to systematically test potential group generators and identify which ones produce trivial results, thereby compromising the entire cryptographic framework. This vulnerability directly affects the confidentiality and integrity aspects of the security model, as it enables attackers to gain unauthorized access to sensitive card information that should remain protected.
Mitigation strategies for CVE-2007-2640 require immediate upgrading to LibTMCG version 1.1.1 or later, which implements proper range checking to exclude trivial group generators from the cryptographic process. Organizations should also conduct comprehensive audits of their cryptographic implementations to identify any other systems that might be using vulnerable versions of the library. The vulnerability aligns with CWE-327, which addresses the use of weak cryptographic algorithms, and can be mapped to ATT&CK technique T1552.001 related to unsecured credentials. Security teams should implement monitoring for suspicious cryptographic parameter generation patterns and establish regular vulnerability assessment procedures to prevent similar issues in other cryptographic libraries. Additionally, system administrators should verify that all cryptographic libraries are regularly updated and that proper input validation mechanisms are in place to prevent similar range checking failures in other security implementations.