CVE-2026-70617: Spacebar Server

High severity, CVSS 8.1. EPSS: 0.4% chance of exploitation in the next 30 days.

Spacebar Server before commit dcfd910 contains a missing authorization vulnerability that allows any authenticated attacker to add themselves to arbitrary group DM channels by sending a PUT request to the channels recipient endpoint without membership verification. Attackers can exploit the unguarded PUT /channels/{channel_id}/recipients/{user_id} handler to join private group DMs, read complete message history, post messages as a participant, and force-add third-party users without their consent.

Affected products

• Spacebar Server Spacebar Server

Published 2026-08-05. Last modified 2026-09-16.