CVE-2026-77164 (GCVE-0-2026-77164)

Vulnerability from cvelistv5 – Published: 2026-09-18 01:26 – Updated: 2026-09-18 19:41
VLAI
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 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.
Severity
6.2 (Medium)
CVSS:3.0/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-09-18 19:40 UTC
CWE
  • CWE-918 - Server-Side Request Forgery (SSRF)
Assigner
hackerone CNA under the mitre root
CNA scorecard D 59/100 over 187 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Nextcloud Server Affected: 31.0.0 , ≤ 32.0.0 (semver)
guessed Create a notification for this product.
Credits
Balvant Chavda (0x0doteth)
Show details on NVD website
To clipboard 

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