CVE-2026-77164: Nextcloud Server

Medium severity, CVSS 6.2. EPSS: 0.2% chance of exploitation in the next 30 days.

Circles' remote-instance signature verification fetches the attacker-supplied keyId URL before trust in the remote instance is established, and explicitly allows local/private addresses for this request, bypassing Nextcloud's core SSRF protections. The public, unauthenticated endpoints POST /apps/circles/event/ and POST /apps/circles/incoming/ reach this code path, allowing any unauthenticated user to force the server to issue a GET request to an internal address. The response body of the internal request is never returned to the requester, so this is blind SSRF: an attacker can determine whether an internal service is reachable, but cannot read its response contents through this endpoint alone.

Affected products

• Nextcloud Server: from 31.0.0, up to and including 32.0.0

Published 2026-09-18. Last modified 2026-09-18.