leancrypto: Integer truncation in X.509 name parser enables certificate identity impersonation

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Summary

CVECVE-2026-34610
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-04-02 18:16:32 UTC
Updated2026-04-02 18:16:32 UTC
DescriptionThe 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.

Risk And Classification

Primary CVSS: v3.1 5.9 MEDIUM from [email protected]

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N

Problem Types: CWE-681 | CWE-681 CWE-681: Incorrect Conversion between Numeric Types

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary5.9MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
3.1CNADECLARED5.9MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA SmuellerDD Leancrypto affected < 1.7.1 Not specified

References

ReferenceSourceLinkTags
github.com/smuellerDD/leancrypto/releases/tag/v1.7.1 [email protected] github.com
github.com/smuellerDD/leancrypto/security/advisories/GHSA-636g-jxv4-v4gr [email protected] github.com
github.com/smuellerDD/leancrypto/commit/5cdcbe12bd6c3d6e87e969972a580b44... [email protected] github.com
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