by Kastro
Paper/Archive/CVE-2026-33640

CVE-2026-33640

outline outline — Outline has a rate limit bypass that allows brute force of email login OTP

EPSS 0.5%public exploitCVSS 9.8
critical.is priorityof 100
48
CVSS 9.8 (NVD)9.8 / 10 × 3029.4Not in CISA KEV+300.0EPSS percentile 41.1.411 × 208.2Exploit: SSVC poc+1010.0SSVC exploitation: poc+100.0
Description · from the CVE record

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.

Affected

ProductAffectedFixed inSource
outline>= 0.86.0, < 1.6.0–CNA

Scores by source

NVD9.8CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
GitHub_M (CNA)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
CISA ADPSSVCExploitation: poc · Automatable: yes · Technical impact: total

References

refgithub.com/outline/outline/security/advisories/GHSA-cwhc-53hw-qqx6refgithub.com/outline/outline/releases/tag/v1.6.0