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Description

Outline is a service that allows for collaborative documentation. Outline implements an Email OTP login flow for users not associated with an Identity Provider. Starting in version 0.86.0 and prior to version 1.6.0, Outline does not invalidate OTP codes based on amount or frequency of invalid submissions, rather it relies on the rate limiter to restrict attempts. Consequently, identified bypasses in the rate limiter permit unrestricted OTP code submissions within the codes lifetime. This allows attackers to perform brute force attacks which enable account takeover. Version 1.6.0 fixes the issue.

PUBLISHED Reserved 2026-03-23 | Published 2026-03-26 | Updated 2026-04-01 | Assigner GitHub_M




CRITICAL: 9.1CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

Problem types

CWE-307: Improper Restriction of Excessive Authentication Attempts

Product status

>= 0.86.0, < 1.6.0
affected

References

github.com/...utline/security/advisories/GHSA-cwhc-53hw-qqx6

github.com/outline/outline/releases/tag/v1.6.0

cve.org (CVE-2026-33640)

nvd.nist.gov (CVE-2026-33640)

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