{"id":"CVE-2026-77164","url":"https://www.cyber-defence.io/tools/cve/CVE-2026-77164","generatedAt":"2026-10-28T05:28:01.174Z","title":"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.","description":"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.\n\nThe 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.","published":"2026-09-18T02:17:08.000Z","lastModified":"2026-09-18T20:17:22.000Z","status":"Deferred","sourceIdentifier":"support@hackerone.com","cvss":{"version":"3.0","score":6.2,"severity":"MEDIUM","vector":"CVSS:3.0/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N"},"cwe":["CWE-918"],"affected":[],"epss":{"score":0.00189,"percentile":0.08428,"date":"2026-10-27","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"low","text":"Lower severity and a low EPSS score (0.19%). Track it; it rarely justifies an emergency change on its own."},"changes":[],"references":[{"url":"https://hackerone.com/reports/3303283","source":"support@hackerone.com"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-77164","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}