CVE-2026-55370 Logto: TOTP code can be replayed within the RFC 6238 validity window (one-time use violation)
Attackers can replay captured TOTP codes within the validity window to bypass MFA and take over accounts if they possess the first factor.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-55370?
CVE-2026-55370 is a medium-severity authentication bypass vulnerability in logto-io logto, published on 10 Jul 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Official 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.
Weakness: CWE-294
Which versions are affected by CVE-2026-55370?
How do I fix CVE-2026-55370?
No fix has been published for CVE-2026-55370 yet. Limit exposure of the affected software until one is available.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-55370 being exploited?
There is no known exploitation of CVE-2026-55370 in the wild and no public exploit code.
Sources
Also known as GHSA-6wj7-c66m-6c82.