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CVE-2026-77164

Server · Vulnerability

CVSS 3.0 6.2 MEDIUMCheck source for fixed versionsKEV status unknown

Original advisory

cve-program · CVE-2026-77164

Published

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.

Read the publisher's advisory

Affected versions, risk and source history

cve-program · CVE-2026-77164

Published

Server

Vendor product

Publisher's version information

Shown as published. These rules are not interpreted as NuGet package version ranges.

{
                    "defaultStatus": "unaffected",
                    "vendor": "Nextcloud",
                    "product": "Server",
                    "versions": [
                        {
                            "version": "31.0.0",
                            "status": "affected",
                            "lessThanOrEqual": "32.0.0",
                            "versionType": "semver"
                        }
                    ]
                }

Original source record · Cite this exact observation · Complete original publisher JSON