CriticalVulnerability
CVE-2026-55640: Nextcloud MCP Server unauthenticated webhook allows forged vector index changes
- Source
- NVD(opens in a new tab)
- Identifier
- CVE-2026-55640
- Published
- Record updated
- Affected
- nextcloud-mcp-server <= 0.117.1
- Fixed in
- 0.117.2
- released June 14, 2026, 72 days before disclosure
- Known exploitation
- Not listed in the CISA Known Exploited Vulnerabilities catalog at the last check.
- EPSS
- 0.7%
Summary
CVE-2026-55640 affects the Nextcloud MCP Server before 0.117.2. The POST /webhooks/nextcloud endpoint in nextcloud_mcp_server/vector/webhook_receiver.py accepts unauthenticated requests when WEBHOOK_SECRET is unset, which is the default, because startup validation does not require it. The payload["user"]["uid"] field from webhook_parser.py is attacker-controlled and used for Qdrant operations without an authenticated-session cross-check, so a network attacker can delete or trigger re-indexing of vector embeddings for any user and destroy the semantic search index with forged deletion events.
Mitigation
Fixed in 0.117.2.
Topics
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