cbcoutinho nextcloud-mcp-server up to 0.117.1 Webhook Receiver webhook_receiver.py handle_nextcloud_webhook uid improper authentication

Summaryinfo

A vulnerability labeled as critical has been found in cbcoutinho nextcloud-mcp-server up to 0.117.1. This impacts the function handle_nextcloud_webhook of the file nextcloud_mcp_server/vector/webhook_receiver.py of the component Webhook Receiver. The manipulation of the argument uid results in improper authentication. This vulnerability was named CVE-2026-55640. The attack may be performed from remote. There is no available exploit.

Detailsinfo

A vulnerability classified as critical has been found in cbcoutinho nextcloud-mcp-server up to 0.117.1. Affected is the function handle_nextcloud_webhook of the file nextcloud_mcp_server/vector/webhook_receiver.py of the component Webhook Receiver. The manipulation of the argument uid with an unknown input leads to a improper authentication vulnerability. CWE is classifying the issue as CWE-287. When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct. This is going to have an impact on integrity, and availability. CVE summarizes:

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.

The advisory is available at github.com. This vulnerability is traded as CVE-2026-55640 since 06/17/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. Technical details are known, but there is no available exploit.

Upgrading to version 0.117.2 eliminates this vulnerability.

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Productinfo

Type

• Artificial Intelligence Software

Vendor

• cbcoutinho

Name

• nextcloud-mcp-server

Version

• 0.117.0
• 0.117.1

Website

• Product: https://github.com/cbcoutinho/nextcloud-mcp-server/

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