# CVE-2026-43890: Missing authorization in outline

> Attackers can subscribe to private documents in other tenants by bypassing authorization checks, leading to unauthorized data access.

- **Severity:** High 7.7 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 11 May 2026
- **Updated:** 13 May 2026
- **Also known as:** GHSA-gf8h-cv9v-q4fw

## What is CVE-2026-43890?

CVE-2026-43890 is a high-severity missing authorization vulnerability in outline, published on 11 May 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official 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.

Weakness: CWE-639 (Authorization Bypass Through User-Controlled Key)

## Which versions are affected by CVE-2026-43890?


## How do I fix CVE-2026-43890?

No fix has been published for CVE-2026-43890 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-43890 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-43890 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-43890 and fix it if it is affected.

What it is: CVE-2026-43890 is a high-severity missing authorization vulnerability in outline, published on 11 May 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-43890 exists.

Affected product: outline. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-43890/ (Markdown: https://insights.sbomify.com/CVE-2026-43890/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-43890
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-43890
- OSV: https://osv.dev/vulnerability/CVE-2026-43890

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-43890/
Summaries are generated and may contain mistakes; the official description above is the record.