{"id":"CVE-2026-77164","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 p…","summary":"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 p…","severity":"medium","cvss":6.2,"cvssVector":"CVSS:3.0/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N","cwe":["CWE-918"],"vendor":"Nextcloud","product":"Server","affected":["Server >= 31.0.0 <= 32.0.0"],"published":"2026-09-18","updated":"2026-09-18","sourceUpdated":"2026-09-18T20:17:22.273","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-77164","references":[{"url":"https://hackerone.com/reports/3303283","label":"support@hackerone.com"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-77164.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-77164"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-77164"}],"tags":["nvd","cve.org","csaf","vex","red-hat"],"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"partial","timestamp":"2026-09-18T19:40:57.953385Z"},"epss":0.00189,"epssPercentile":0.08428,"ingestedAt":"2026-09-18T01:33:24.269Z","scores":{"nvd":6.2,"vendor":5.3},"slug":"CVE-2026-77164","body":"## Overview\n\nCircles' 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.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n## Vendor advisories\n\n- **Red Hat VEX** · updated 2026-09-23 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-77164.json)","depth":"sunlit","depthScore":34,"depthScoreParts":{"impact":34.1,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}