Certificate identity impersonation via CN length truncation
Published Apr 2, 2026 · Updated Apr 2, 2026
Incorrect numeric conversion in leancrypto before 1.7.1 allows remote attackers to impersonate identities through crafted X.509 names. lc_x509_extract_name_segment() narrows the size_t name length to uint8_t, wrapping a victim CN plus 256 padding bytes to the victim CN length. Exploitation requires a validly signed crafted certificate whose CN begins with the victim CN; affected PKCS#7, chain-matching, or code-signing checks then accept the forged identity.
Summary
What happened
Incorrect numeric conversion in leancrypto before 1.7.1 allows remote attackers to impersonate identities through crafted X.509 names. lc_x509_extract_name_segment() narrows the size_t name length to uint8_t, wrapping a victim CN plus 256 padding bytes to the victim CN length. Exploitation requires a validly signed crafted certificate whose CN begins with the victim CN; affected PKCS#7, chain-matching, or code-signing checks then accept the forged identity.
The record
- CVE
- CVE-2026-34610
- Published
- Apr 2, 2026
- Updated
- Apr 2, 2026
- Vendor
- smuellerDD
- Product
- leancrypto
- Classifications
- CWE-681, T1649
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Apr 2, 2026CVE publishedPublication date reported by the CVE source.
- Apr 2, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
Compare your product and version with the public record. A matching version still requires validation against your environment.
Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 1.7.1
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
No public exploit references are available in this record.
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
See the directory against your own environment.
Your stack
Check the software in your environment
Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.
Book a demo