Vulnerability in Leancrypto
CVE-2026-34610
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 5.9 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N.
EPSS exploit prediction
EPSS: 0.003 (16.3th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 16th percentile — 16.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.003 · change: +0.001
Affected products
- Leancrypto
- Smuellerdd Leancrypto — versions < 1.7.1
Weakness classification (CWE)
References
- github.com/smuellerDD/leancrypto/security/advisories/GHSA-636g-jxv4-v4gr (Vendor Advisory)
- github.com/smuellerDD/leancrypto/commit/5cdcbe12bd6c3d6e87e969972a580b44a74c3a6a (Patch)
- github.com/smuellerDD/leancrypto/releases/tag/v1.7.1 (Product, Release Notes)
Frequently asked questions
- What is CVE-2026-34610?
- CVE-2026-34610 is a medium-severity vulnerability in Leancrypto, classified under Incorrect Conversion between Numeric Types. CVSS score: 5.9/10. Published 2026-04-02.
- How severe is CVE-2026-34610?
- Medium severity. CVSS v3 base score is 5.9 out of 10.