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Vulnerability record · CVE-2026-33640 · published 26 March 2026

CVE-2026-33640: Getoutline outline improper restriction of authentication attempts vulnerability

Getoutline · Outline

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.

9.1 CVSS 4.0 Critical EPSS 0.55% · top 56.6% CWE-307 · Improper restriction of authentication attempts
9.1CVSS 4.0 base score
0.55%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
2References, 1 tagged exploit
17 Jun 2026Last modified by NVD

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.

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/outline/outline/releases/tag/v1.6.0 Release Notes
https://github.com/outline/outline/security/advisories/GHSA-cwhc-53hw-qqx6 ExploitVendor Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

8.8CVE-2026-24901Getoutline outline insecure direct object reference vulnerabilityOutline is a service that allows for collaborative documentation. Prior to 1.4.0, an Insecure Direct Object Reference (IDOR) vulnerability in the doc…EPSS 0.31%8.8CVE-2024-37829Getoutline outline vulnerabilityAn issue in Outline <= v0.76.1 allows attackers to execute a session hijacking attack via user interaction with a crafted magic sign-in link.EPSS 0.74%8.5CVE-2023-54331Getoutline outline unquoted search path vulnerabilityOutline 1.6.0 contains an unquoted service path vulnerability that allows local attackers to potentially execute arbitrary code with elevated system …EPSS 0.22%7.7CVE-2026-41649Getoutline outline insecure direct object reference vulnerabilityOutline is a service that allows for collaborative documentation. The `shares.create` API endpoint starting in version 0.86.0 and prior to version 1.…EPSS 0.42%7.6CVE-2025-64487Getoutline outline improper privilege management vulnerabilityOutline is a service that allows for collaborative documentation. Prior to 1.1.0, a privilege escalation vulnerability exists in the Outline document…EPSS 0.20%6.9CVE-2025-68663Getoutline outline improper authentication vulnerabilityOutline is a service that allows for collaborative documentation. Prior to 1.1.0, a vulnerability was found in Outline's WebSocket authentication mec…EPSS 0.25%6.8CVE-2025-58351Getoutline outline cross-site scripting vulnerabilityOutline is a service that allows for collaborative documentation. In versions 0.72.0 through 0.83.0, Outline introduced a feature which facilitates l…EPSS 0.39%6.5CVE-2026-44695Getoutline outline cross-site request forgery vulnerabilityOutline is a service that allows for collaborative documentation. Prior to 1.7.1, the Slack integration callback for GET /auth/slack.post accepts an …EPSS 0.15%

Source: NIST National Vulnerability Database (record CVE-2026-33640), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.