Vulnerability · Published Apr 2, 2026 · Assigned by GitHub_M
CVE-2026-34610leancrypto: Integer truncation in X.509 name parser enables certificate identity impersonation
Medium 5.9
In plain English
A medium-severity security flaw in leancrypto from smuellerDD. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 6% of all known vulnerabilities).
Official 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.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| smuellerDD | leancrypto | < 1.7.1 |
Weakness: CWE-681 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N