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.
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.
Metrics
Affected Vendors & Products
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Advisories
No advisories yet.
Fixes
Solution
No solution given by the vendor.
Workaround
No workaround given by the vendor.
References
| Link | Providers |
|---|---|
| https://hackerone.com/reports/3303283 |
|
History
Fri, 18 Sep 2026 01:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| 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. 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. | |
| Weaknesses | CWE-918 | |
| References |
| |
| Metrics |
cvssV3_0
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Projects
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MITRE
Status: PUBLISHED
Assigner: hackerone
Published:
Updated: 2026-09-18T01:26:04.650Z
Reserved: 2026-08-20T15:00:00.606Z
Link: CVE-2026-77164
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-09-18T02:17:07.510
Modified: 2026-09-18T02:17:07.510
Link: CVE-2026-77164
Redhat
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OpenCVE Enrichment
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Weaknesses