# CVE-2026-55370: Logto TOTP authentication bypass via capture-replay

Source: https://junglewise.ai/threats/cve-2026-55370-logto-totp-authentication-bypass-via-capture-replay  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-10. Updated: 2026-07-10  
License: CC BY 4.0 with a link back

CVE-2026-55370 · Severity: medium · CVSS 6.4 · Published 2026-07-10

Logto, an open-source authentication platform for applications, was found to have a flaw in its multi-factor authentication (MFA) process. The system failed to properly invalidate one-time passwords (TOTP) after they were used, allowing a code to be reused multiple times within its short validity window. If an attacker manages to steal a user's primary password and intercept a live MFA code, they could potentially log in as that user even if MFA is enabled.

Technologies: [Logto](https://junglewise.ai/threats/technologies/logto). Vendors: [Logto](https://junglewise.ai/threats/vendors/logto).

## Quick answers

**Is CVE-2026-55370 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-55370 being exploited in the wild.

**How severe is CVE-2026-55370?** Medium severity, with a CVSS score of 6.4, published 10 July 2026.

**Which products and versions are affected?** Logto < 1.41.0.

**Is there a fix for CVE-2026-55370?** A patch was published on 2026-06-30: Version 1.41.0 released containing the fix. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-55370 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-55370?** Check whether you run Logto at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

Logto's TOTP verification mechanism was vulnerable to replay attacks because it utilized a stateless check without persisting or comparing the time-step counter. Specifically, the verifier used the 'otplib' library with a window setting of 1 but did not track whether a specific code had already been successfully validated. An attacker who has obtained a victim's primary credentials and can intercept a valid TOTP code (e.g., via man-in-the-middle or shoulder surfing) can replay that code to satisfy the MFA requirement as long as the code remains within the 30-60 second acceptance window. The fix, introduced in version 1.41.0, involves recording the last-used time-step counter and rejecting any subsequent attempts using the same or an older counter.

## Affected products

- logto-io Logto < 1.41.0

## Timeline

- 2026-06-29: disclosed: Pull request submitted to fix the replay issue.
- 2026-06-30: patched: Version 1.41.0 released containing the fix.
- 2026-07-10: advisory: CVE-2026-55370 published.

## References

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

## Related threats

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- [Logto server-side request forgery in OIDC connector creation](https://junglewise.ai/threats/cve-2026-82263-logto-server-side-request-forgery-in-oidc-connector-creation)
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- [Logto account takeover via improper identifier normalization](https://junglewise.ai/threats/cve-2026-15617-logto-account-takeover-via-improper-identifier-normalization)