CVE-2026-77164
mediumpriority · track · 0EPSS 0.002 · 8 %ileUSEPSS · scored 2026-10-27
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.
cvss
Technical severity, 0–10. One row per scoring source.
base score 0–10 · higher = more severe · hover a vector to decode
ssvc
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weaknesses
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affected products (1)
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advisories (1)
Vendor and ecosystem advisories describing this.
- BIT-nextcloud-2026-771642026-09-25vendor · osvUS
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.
sources
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references (1) nvd
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