CVE-2026-55640: Nextcloud MCP Server is a production-ready MCP server that connects AI assistants to a Nextcloud instance. Prior to 0.11
Summary
Nextcloud MCP Server (a tool that connects AI assistants to Nextcloud file storage) had a security flaw in versions before 0.117.2 where the webhook endpoint (a way for systems to send automated messages) didn't require authentication by default. This allowed attackers to send fake requests that could delete or mess up vector embeddings (the numerical representations of data used for semantic search, which helps find files by meaning rather than keywords), harming the search index for any user.
Solution / Mitigation
Update to version 0.117.2 or later. According to the source, 'This issue is fixed in version 0.117.2.'
Vulnerability Details
9.1(critical)
EPSS: 0.0%
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
network
low
none
none
August 25, 2026
Classification
Affected Vendors
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Original source: https://nvd.nist.gov/vuln/detail/CVE-2026-55640
First tracked: August 25, 2026 at 02:10 PM
Classified by LLM (prompt v3) · confidence: 95%