Vulnerability in Getoutline Outline
CVE-2026-33640
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 · last modified .
CVSS v3 metric
CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.005 (43.5th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 43rd percentile — 43.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.005 · newest: 0.005 · change: +0.001
Affected products
- Getoutline Outline
- Outline — versions >= 0.86.0, < 1.6.0
Weakness classification (CWE)
References
- github.com/outline/outline/security/advisories/GHSA-cwhc-53hw-qqx6 (Exploit, Vendor Advisory)
- github.com/outline/outline/releases/tag/v1.6.0 (Release Notes)
Frequently asked questions
- What is CVE-2026-33640?
- CVE-2026-33640 is a critical-severity vulnerability in Getoutline Outline, classified under Improper Restriction of Excessive Authentication Attempts. CVSS score: 9.8/10. Published 2026-03-26.
- How severe is CVE-2026-33640?
- Critical severity. CVSS v3 base score is 9.8 out of 10.