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CVE-2026-43890— Outline: IDOR in subscriptions.create allows cross-tenant subscription on private documents (sibling of GHSA-23jj-rp48-w7q7)

Quick assessment

Affected
outline outline
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Outline是Outline开源的一个知识库。 Outline 0.84.0版本至1.7.0版本存在安全漏洞，该漏洞源于subscriptions.create API端点存在损坏的授权模式，当同时提供collectionId和documentId时，路由处理程序仅授权集合分支，而下游subscriptionCreator命令针对未验证的documentId写入订阅，导致订阅记录将攻击者用户固定到攻击者无读取权限的受害者文档上。

CVSS 7.7 · High EPSS 0.34% · P25

Possible ATT&CK Techniques 1 AI

T1078 · Valid Accounts

Affected Version Matrix 1

VendorProduct Version RangeStatus
outline outline >= 0.82.1, < 1.7.1 affected
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I. Basic Information for CVE-2026-43890

Vulnerability Information
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Vulnerability Title
Outline: IDOR in subscriptions.create allows cross-tenant subscription on private documents (sibling of GHSA-23jj-rp48-w7q7)
Source: CVE Program / CVE List V5
Vulnerability Description
Outline is a service that allows for collaborative documentation. From 0.84.0 to 1.7.0, the subscriptions.create API endpoint in server/routes/api/subscriptions/subscriptions.ts exhibits a broken authorization pattern. When both collectionId and documentId are supplied in the request, the route handler authorizes ONLY the collection branch (line 125 if (collectionId)), while the downstream subscriptionCreator command at server/commands/subscriptionCreator.ts writes the subscription against the documentId (which was never validated). The result is a subscription record pinning the attacker's user to a victim document the attacker has no read access to, on any team in the instance. The schema (server/routes/api/subscriptions/schema.ts) only enforces "at least one of collectionId/documentId" via .refine() — it does NOT enforce mutual exclusivity, so passing both is a valid, schema-conforming request. This vulnerability is fixed in 1.7.1.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
通过用户控制密钥绕过授权机制
Source: CVE Program / CVE List V5
Vulnerability Title
Outline 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Outline是Outline开源的一个知识库。 Outline 0.84.0版本至1.7.0版本存在安全漏洞，该漏洞源于subscriptions.create API端点存在损坏的授权模式，当同时提供collectionId和documentId时，路由处理程序仅授权集合分支，而下游subscriptionCreator命令针对未验证的documentId写入订阅，导致订阅记录将攻击者用户固定到攻击者无读取权限的受害者文档上。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
outline outline >= 0.82.1, < 1.7.1 -

II. Public POCs for CVE-2026-43890

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III. Intelligence Information for CVE-2026-43890

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Vendor Advisories for CVE-2026-43890 (1)

Same Patch Batch · outline · 2026-05-11 · 6 CVEs total

CVE-2026-43888 8.7 HIGH Outline: Zip Extraction Path Escape via PATH_MAX Truncation in Collection Import
CVE-2026-43886 8.2 HIGH Outline: OAuth Scope Validation Logic Error Allows Privilege Escalation to Wildcard API Ac
CVE-2026-43887 7.3 HIGH Outline: Stored XSS via Comment Mentions
CVE-2026-43889 6.5 MEDIUM Outline: Unauthorized Document Publication via Mixed collectionId+documentId Share
CVE-2026-44695 5.8 MEDIUM Outline: Slack OAuth state can link a victim Outline account to an attacker Slack identity

IV. Related Vulnerabilities

Same product: outline
Same vendor: outline
Same weakness: CWE-639

V. Comments for CVE-2026-43890

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