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TI-2026-26021 Aliases CVE-2026-33640

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

Priority HIGH 80CWE-307Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Attack requirements
Present
Impact type
Security bypass
Confidentiality · integrity · availability
High · High · None
Fix status
Fixed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA. Impact type from CWE-307.

Summary

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.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00476 41st percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix Fixed outline (outline): 1.6.0

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
Yes
Technical impact
Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
outlineoutline0.86.0 to before 1.6.01.6.0Patch availableCNA
  • outline Vendoroutline Affected 0.86.0 to before 1.6.0 Fixed in 1.6.0 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:getoutline:outline:*:*:*:*:*:*:*:*0.86.0 to before 1.6.0Vulnerableoutline
  • cpe:2.3:a:getoutline:outline:*:*:*:*:*:*:*:* Versions 0.86.0 to before 1.6.0 Vulnerable ·outline

Remediation

  • Fix · CNA outline (outline) Fixed in 1.6.0

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-33640

References

Exploit 1

Other 1

  • TI-2026-20086 Outline's IDOR allows unauthorized viewing and seizing of private deleted drafts CVSS 3.1HIGH 8.8
  • TI-2024-25167 An issue in Outline <= v0.76.1 allows attackers to execute a session hijacking attack via… CVSS 3.1HIGH 8.8
  • TI-2026-30168 Outline has IDOR in document share creation that allows unauthorized access to private documents across workspaces CVSS 3.1HIGH 7.7
  • TI-2024-27038 Stored Cross-site Scripting (XSS) vulnerability in Outline editor CVSS 3.1HIGH 7.3
  • TI-2026-32586 Outline: Slack OAuth state can link a victim Outline account to an attacker Slack identity CVSS 3.1MEDIUM 6.5
  • TI-2024-25168 An issue in Outline <= v0.76.1 allows attackers to redirect a victim user to a malicious… CVSS 3.1MEDIUM 6.1
See all 14 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences