CVE-2026-55370: CWE-294: Authentication Bypass by Capture-replay in logto-io logto
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.
AI Analysis
Technical Summary
CVE-2026-55370 is an authentication bypass vulnerability in logto-io's Logto product affecting versions before 1.41.0. The vulnerability arises because the TOTP verification used otplib's stateless check with a window of 1 and did not persist or compare the accepted TOTP time-step counter. Consequently, a valid TOTP code could be reused (replayed) within the acceptance window, enabling an attacker who has the victim's first factor and captures a live TOTP value to bypass multi-factor authentication. This flaw violates proper TOTP usage as defined in RFC 6238. The vulnerability is addressed in Logto version 1.41.0.
Potential Impact
An attacker who has compromised the victim's primary authentication factor and can capture a valid TOTP code can replay that code within the acceptance window to bypass multi-factor authentication. This leads to unauthorized access with high confidentiality and integrity impact, as the attacker can impersonate the victim without needing to generate a fresh TOTP code. Availability is not impacted.
Mitigation Recommendations
Upgrade Logto to version 1.41.0 or later, where this vulnerability is fixed. No other mitigation is indicated. Patch status is not explicitly stated but the vendor fixed the issue in 1.41.0, so upgrading to this version or later is the recommended remediation.
CVE-2026-55370: CWE-294: Authentication Bypass by Capture-replay in logto-io logto
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.
CVSS v3.1
Score 6.4medium
Affected software
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Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-55370 is an authentication bypass vulnerability in logto-io's Logto product affecting versions before 1.41.0. The vulnerability arises because the TOTP verification used otplib's stateless check with a window of 1 and did not persist or compare the accepted TOTP time-step counter. Consequently, a valid TOTP code could be reused (replayed) within the acceptance window, enabling an attacker who has the victim's first factor and captures a live TOTP value to bypass multi-factor authentication. This flaw violates proper TOTP usage as defined in RFC 6238. The vulnerability is addressed in Logto version 1.41.0.
Potential Impact
An attacker who has compromised the victim's primary authentication factor and can capture a valid TOTP code can replay that code within the acceptance window to bypass multi-factor authentication. This leads to unauthorized access with high confidentiality and integrity impact, as the attacker can impersonate the victim without needing to generate a fresh TOTP code. Availability is not impacted.
Mitigation Recommendations
Upgrade Logto to version 1.41.0 or later, where this vulnerability is fixed. No other mitigation is indicated. Patch status is not explicitly stated but the vendor fixed the issue in 1.41.0, so upgrading to this version or later is the recommended remediation.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-06-16T18:57:40.181Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a51500968715ace431e0bb9
Added to database: 07/10/2026, 20:03:21 UTC
Last enriched: 07/10/2026, 20:18:43 UTC
Last updated: 07/10/2026, 22:38:12 UTC
Views: 7
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