Bug 2454585 (CVE-2026-34610)

Summary: CVE-2026-34610 leancrypto: leancrypto: Identity impersonation via integer overflow in X.509 Common Name processing
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Priority: medium    
Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was found in the leancrypto cryptographic library. A remote attacker can exploit an integer overflow vulnerability in the lc_x509_extract_name_segment() function when processing the Common Name (CN) field of an X.509 certificate. By crafting a specially designed certificate, an attacker can cause the system to incorrectly match their certificate's CN with a victim's, leading to identity impersonation. This can impact the integrity of PKCS#7 (Public-Key Cryptography Standards #7) verification, certificate chain matching, and code signing processes.
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Description OSIDB Bzimport 2026-04-02 19:02:42 UTC 
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.