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CVE-2026-34610— leancrypto: Integer truncation in X.509 name parser enables certificate identity impersonation

Quick assessment

Affected
smuellerDD leancrypto
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Lean Crypto Library是smuellerDD个人开发者的一个轻量级抗量子密码算法库。 Lean Crypto Library 1.7.1之前版本存在安全漏洞，该漏洞源于lc_x509_extract_name_segment函数将size_t转换为uint8_t时存在整数溢出，可能导致身份冒充。

CVSS 5.9 · Medium EPSS 0.26% · P16
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I. Basic Information for CVE-2026-34610

Vulnerability Information
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Vulnerability Title
leancrypto: Integer truncation in X.509 name parser enables certificate identity impersonation
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
数值类型间的不正确转换
Source: CVE Program / CVE List V5
Vulnerability Title
Lean Crypto Library 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Lean Crypto Library是smuellerDD个人开发者的一个轻量级抗量子密码算法库。 Lean Crypto Library 1.7.1之前版本存在安全漏洞，该漏洞源于lc_x509_extract_name_segment函数将size_t转换为uint8_t时存在整数溢出，可能导致身份冒充。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
smuellerDD leancrypto < 1.7.1 -

II. Public POCs for CVE-2026-34610

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III. Intelligence Information for CVE-2026-34610

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Patches & Fixes for CVE-2026-34610 (2)

Vendor Advisories for CVE-2026-34610 (1)

IV. Related Vulnerabilities

Same weakness: CWE-681

V. Comments for CVE-2026-34610

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