{"cve":"CVE-2026-45018","nvd":{"published":"2026-08-25T20:16:55.720","modified":"2026-09-09T21:07:31.353","status":"Deferred","description":"Chainlit is a Python framework for building production-ready conversational AI applications. From 2.4.0rc0 until 2.12.0, Chainlit deployments with features.mcp.enabled set to true in .chainlit/config.toml expose the POST /mcp endpoint without requiring authentication. For stdio transport, the endpoint accepts a user-controlled fullCommand string. The validate_mcp_command() function in backend/chainlit/mcp.py checks only the executable name against config.features.mcp.stdio.allowed_executables and passes unchecked arguments to StdioServerParameters in backend/chainlit/server.py. Because npx supports the -c argument, an attacker can execute arbitrary shell commands with the privileges of the Chainlit process. If allowed_executables is unset, its None default is treated as allowing every executable. This issue is fixed in version 2.12.0.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","score":9.8},"cwes":["CWE-78"],"references":["https://github.com/Chainlit/chainlit/blob/2.12.0/docs/security-advisory-2026-mcp.md#spl-2026-001--command-injection-via-mcp-stdio","https://github.com/Chainlit/chainlit/commit/0565fd0eccb915fce159929598b053ed79f6e0c9","https://github.com/Chainlit/chainlit/releases/tag/2.12.0","https://github.com/Chainlit/chainlit/security/advisories/GHSA-w3fx-mc44-mf6j","https://github.com/Chainlit/chainlit/security/advisories/GHSA-w3fx-mc44-mf6j"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:50:17.453294893+00:00"},"epss":{"cve":"CVE-2026-45018","score":0.01086,"percentile":0.65293,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-w3fx-mc44-mf6j","url":"https://osv.dev/vulnerability/GHSA-w3fx-mc44-mf6j","summary":"Chainlit has command injection via MCP stdio transport that allows unauthenticated remote code execution","modified":"2026-09-10T12:26:01.565580392Z","packages":[{"ecosystem":"PyPI","name":"chainlit","purl":"pkg:pypi/chainlit","ranges":[">=2.4.0rc0 <2.12.0"],"fixed":["2.12.0"]}]},{"id":"PYSEC-2026-3812","url":"https://osv.dev/vulnerability/PYSEC-2026-3812","summary":"Chainlit has command injection via MCP stdio transport that allows unauthenticated remote code execution","modified":"2026-09-10T12:15:06.248346122Z","packages":[{"ecosystem":"PyPI","name":"chainlit","purl":"pkg:pypi/chainlit","ranges":[">=2.4.0rc0 <2.12.0"],"fixed":["2.12.0"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}