CVE-2026-43890Public exploitNetwork attack vector

Cross-tenant subscriptions via mismatched authorization branches

Published May 11, 2026 · Updated May 11, 2026

Authorization bypass in Outline 0.82.1 through 1.7.0 allows remote authenticated users to subscribe to private documents. The subscriptions.create route authorizes collectionId when both identifiers are supplied, but subscriptionCreator prioritizes and writes the unchecked documentId. Any team member with a readable collection and a target document UUID can receive document-title, modifier-identity, and update-frequency notifications without reading the document body.

CVSS severity7.7
High
EPSS probability0.21%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authorization bypass in Outline 0.82.1 through 1.7.0 allows remote authenticated users to subscribe to private documents. The subscriptions.create route authorizes collectionId when both identifiers are supplied, but subscriptionCreator prioritizes and writes the unchecked documentId. Any team member with a readable collection and a target document UUID can receive document-title, modifier-identity, and update-frequency notifications without reading the document body.

The record

CVE
CVE-2026-43890
Published
May 11, 2026
Updated
May 11, 2026
Vendor
Outline
Product
Outline
Classifications
CWE-639, T1190
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. May 11, 2026CVE publishedPublication date reported by the CVE source.
  2. May 11, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 0.82.1, < 1.7.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Outline · Outlineversion=>= 0.82.1, < 1.7.1

Published CVSS scores

7.7GitHub CNACVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N
4.4GitHub Security AdvisoryCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-639Authorization Bypass Through User-Controlled Key
T1190Exploit Public-Facing Application

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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