CVE-2026-55640: 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…

PriorityP263critical9.1CVSS 3.1

AVNACLPRNUINSUCNIHAH

EPSS

0.73%

52.4th percentile

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.

Affected

2 ranges

Vendor	Product	Version range	Fixed in
cbcoutinho	nextcloud-mcp-server	< 0.117.2	0.117.2
cbcoutinho	nextcloud-mcp-server	>= 0 < 0.117.2	0.117.2

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