TI-2026-26856 Aliases CVE-2026-34610

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

LOW 26CWE-681Published 2026-04-02 · Updated 2026-04-03

Key facts

Attack vector: Network
Privileges required: None
User interaction: None
Attack complexity: High
Impact type: —
Confidentiality · integrity · availability: None · High · None
Fix status: Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA.

Summary

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.00169 6th percentileScored 2026-11-07

Fix Fixed leancrypto (smuellerDD): 1.7.1

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: None
Automatable: No
Technical impact: Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
smuellerDD	leancrypto	before 1.7.1	1.7.1	Patch available	CNA

leancrypto VendorsmuellerDD Affected before 1.7.1 Fixed in 1.7.1 Patch available CNA

CPE configurations NVD · 1

CPE	Versions	Role	Vendor
cpe:2.3:a:leancrypto:leancrypto::::::::	before 1.7.1	Vulnerable	Leancrypto

cpe:2.3:a:leancrypto:leancrypto:*:*:*:*:*:*:*:* Versions before 1.7.1 Vulnerable ·Leancrypto

Remediation

Fix · CNA leancrypto (smuellerDD) Fixed in 1.7.1

Vendor assessments

Red Hat

Red Hat's page for this CVE →

Not affected: 1 product

Red Hat

Timeline

2026-10-02 Threatist record created from CVE-2026-34610

References

TI-2026-49900 Libkcapi: memory corruption via uncanceled aio requests on error in libkcapi's one-shot aio path CVSS 3.1HIGH 7.3
TI-2026-49899 Libkcapi: iv reuse in libkcapi one-shot symmetric cipher chunking causes cipher state reset across chunk boundaries CVSS 3.1MEDIUM 6.5
TI-2026-49901 Infinite loop in Stephan Muelle libkcapi CVSS 3.1MEDIUM 5.1

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences