The leancrypto library is a cryptographic library that exclusively contains only PQC-resistant cryptographic algorithms. Prior to version 1.7.1, lc_x509_extract_name_segment() casts size_t vlen to uint8_t when storing the Common Name (CN) length. An attacker who crafts a certificate with CN = victim's CN + 256 bytes padding gets cn_size = (uint8_t)(256 + N) = N, where N is the victim's CN length.
The first N bytes of the attacker's CN are the victim's identity. After parsing, the attacker's certificate has an identical CN to the victim's — enabling identity impersonation in PKCS#7 verification, certificate chain matching, and code signing. This issue has been patched in version 1.7.1.
Attack Parameters
Attack Vector
Network
Can be exploited remotely
Attack Complexity
High
Difficult to exploit
Privileges Required
None
No privileges needed
User Interaction
None
No user interaction needed
Impact Assessment
Confidentiality
None
No data leak
Integrity
High
Complete data modification
Availability
None
No disruption
CVSS Vector v3.1
Weakness Type (CWE)
Vulnerable Products
smuellerdd:leancrypto
References 3
https://github.com/smuellerDD/leancrypto/security/advisories/GHSA-636g-jxv4-v4gr
https://github.com/smuellerDD/leancrypto/security/advisories/GHSA-636g-jxv4-v4gr
https://github.com/smuellerDD/leancrypto/commit/5cdcbe12bd6c3d6e87e969972a580b4…
https://github.com/smuellerDD/leancrypto/commit/5cdcbe12bd6c3d6e87e969972a580b44a74c3a6a
https://github.com/smuellerDD/leancrypto/releases/tag/v1.7.1
https://github.com/smuellerDD/leancrypto/releases/tag/v1.7.1