CVE-2026-55370: Logto-Io Logto

Medium severity, CVSS 6.4. EPSS: 0.3% chance of exploitation in the next 30 days.

Logto is the modern, open-source auth infrastructure for SaaS and AI apps. Prior to 1.41.0, Logto's existing TOTP verification accepted a successfully used TOTP code again while the code remained inside the RFC 6238 acceptance window because the verifier used otplib's stateless check with window = 1 and did not persist or compare the accepted TOTP time-step counter. An attacker who has the victim's first factor and captures a live TOTP value can replay that value to satisfy MFA during the same acceptance window. This issue is fixed in version 1.41.0.

Affected products

• Logto-Io Logto: before 1.41.0 (fixed in 1.41.0)

Published 2026-07-10. Last modified 2026-07-13.