CVE-2026-34610: leancrypto

Vulnerability summary

CVE-2026-34610 is a medium (CVSS 5.9) vulnerability in leancrypto. EPSS estimates a 0.26% chance of exploitation in the next 30 days, higher than 16.4% of scored vulnerabilities.

Timeline

1. 02-04-2026
   PublishedVulnerability first disclosed.
2. 03-04-2026
   Last modifiedVulnerability information updated.

Description

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.

• CWE-681Incorrect Conversion between Numeric TypesWhen converting from one data type to another, such as long to integer, data can be omitted or translated in a way that produces unexpected values. If the resulting values are used in a sensitive context, then dangerous behaviors may occur.