{"id":"CVE-2026-55640","url":"https://www.cyber-defence.io/tools/cve/CVE-2026-55640","generatedAt":"2026-10-28T06:13:25.313Z","title":"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…","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.","published":"2026-08-25T16:16:56.000Z","lastModified":"2026-09-09T21:07:31.000Z","status":"Deferred","sourceIdentifier":"security-advisories@github.com","cvss":{"version":"3.1","score":9.1,"severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H"},"cwe":["CWE-306"],"affected":[],"epss":{"score":0.0073,"percentile":0.54068,"date":"2026-10-27","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"high","text":"High impact if exploited, but EPSS currently rates exploitation as unlikely (0.73%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit."},"changes":[],"references":[{"url":"https://github.com/cbcoutinho/nextcloud-mcp-server/commit/4fc2b10945108cf1008ec9698291de6706ffcb73","source":"security-advisories@github.com"},{"url":"https://github.com/cbcoutinho/nextcloud-mcp-server/security/advisories/GHSA-8vh3-g2qg-2h2c","source":"security-advisories@github.com"},{"url":"https://github.com/cbcoutinho/nextcloud-mcp-server/tree/v0.117.2","source":"security-advisories@github.com"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-55640","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}