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Medium · 6.4 CVE-2026-55370 EUVD-2026-43011

Logto: TOTP code can be replayed within the RFC 6238 validity window (one-time use violation)

Published Jul 10, 2026 · Updated Jul 10, 2026 · Assigned by GitHub_M

Description

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

VendorProductAffectedFixed
logto-io logto < 1.41.0 —

References