CVE Catalog

CVE-2026-77164

MediumCVSS 6.2
Published: Updated: Translated: NVD NIST

Exploitation Probability (EPSS)

Low risk
0.13%

3th percentile - higher than 3% of all known CVEs

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 is never returned, making this a blind SSRF.

Risk Assessment

An unauthenticated attacker can scan the internal network and determine the reachability of internal services. Although responses cannot be read, this allows mapping infrastructure and preparing further attacks.

Recommendation

Upgrade the Circles app to a version that blocks local/private addresses in keyId verification. Until then, consider restricting network access to Circles endpoints.

Related vulnerabilities

Original NVD description (English source)

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.

Vulnerability data from NVD (NIST) · CISA KEV · EPSS