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.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
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
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.
Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.
Is CVE-2026-43890 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-43890 exists.
Sources
Also known as GHSA-gf8h-cv9v-q4fw.