{"cve":"CVE-2026-55640","nvd":{"published":"2026-08-25T16:16:55.810","modified":"2026-09-09T21:07:31.353","status":"Deferred","description":"Nextcloud MCP Server is a production-ready MCP server that connects AI assistants to a Nextcloud instance. Prior to 0.117.2, the POST /webhooks/nextcloud endpoint in nextcloud_mcp_server/vector/webhook_receiver.py has no authentication by default because WEBHOOK_SECRET defaults to None and startup validation does not require it. When WEBHOOK_SECRET is unset, handle_nextcloud_webhook() accepts unauthenticated requests. The payload[\"user\"][\"uid\"] field parsed in nextcloud_mcp_server/vector/webhook_parser.py is attacker-controlled and is used without an authenticated-session cross-check for Qdrant operations, allowing a network attacker to delete or trigger re-indexing of vector embeddings for any user and to destroy the semantic search index by sending forged deletion events. This issue is fixed in version 0.117.2.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H","score":9.1},"cwes":["CWE-306"],"references":["https://github.com/cbcoutinho/nextcloud-mcp-server/commit/4fc2b10945108cf1008ec9698291de6706ffcb73","https://github.com/cbcoutinho/nextcloud-mcp-server/security/advisories/GHSA-8vh3-g2qg-2h2c","https://github.com/cbcoutinho/nextcloud-mcp-server/tree/v0.117.2"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:50:17.453294893+00:00"},"epss":{"cve":"CVE-2026-55640","score":0.0073,"percentile":0.54291,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-8vh3-g2qg-2h2c","url":"https://osv.dev/vulnerability/GHSA-8vh3-g2qg-2h2c","summary":"nextcloud-mcp-server: Unauthenticated `POST /webhooks/nextcloud` allows arbitrary vector data deletion when `WEBHOOK_SECRET` is unset ( default )","modified":"2026-09-10T12:26:01.466673851Z","packages":[{"ecosystem":"PyPI","name":"nextcloud-mcp-server","purl":"pkg:pypi/nextcloud-mcp-server","ranges":["<0.117.2"],"fixed":["0.117.2"]}]},{"id":"PYSEC-2026-3866","url":"https://osv.dev/vulnerability/PYSEC-2026-3866","summary":"nextcloud-mcp-server: Unauthenticated `POST /webhooks/nextcloud` allows arbitrary vector data deletion when `WEBHOOK_SECRET` is unset ( default )","modified":"2026-09-10T12:15:18.811964337Z","packages":[{"ecosystem":"PyPI","name":"nextcloud-mcp-server","purl":"pkg:pypi/nextcloud-mcp-server","ranges":["<0.117.2"],"fixed":["0.117.2"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}