Is CVE-2026-43890 actively exploited?

No active exploitation of CVE-2026-43890 has been confirmed so far. Continue monitoring, as exploit status can change.

Can CVE-2026-43890 be exploited remotely?

Yes. CVE-2026-43890 is exploitable remotely over the network (CVSS attack vector: Network).

What is the CVSS score of CVE-2026-43890?

CVE-2026-43890 has a CVSS score of 7.7 (HIGH).

HOME VULNERABILITIESCVE-2026-43890

HIGH

CVE-2026-43890

CWE-639Published: May 11, 2026· Updated: May 13, 2026

7.7

CVSS v3.1

EPSS:0.03%probability of exploitation in 30 daysPercentile:8.1th

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.

NVD Source

Technical Analysis

CVE-2026-43890 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

Exploitation requires low privileges, which limits the exposure to scenarios where an attacker has already gained initial access.

A successful exploit results in complete confidentiality breach (data exposure), with a CVSS base score of 7.7.

The vulnerability has a "Changed" scope, meaning successful exploitation can impact components beyond the vulnerable component itself — such as the host operating system or adjacent services.