{"id":"CVE-2026-45018","aliases":[],"url":"https://o3.security/vulnerability/CVE-2026-45018","summary":"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…","details":"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.","published":"2026-08-25T20:16:55.720","modified":"2026-08-25T20:16:55.720","cvss":{"score":9.8,"severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"},"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[],"fix":{"url":"https://github.com/Chainlit/chainlit/commit/0565fd0eccb915fce159929598b053ed79f6e0c9","label":"Chainlit/chainlit@0565fd0"},"references":[{"type":"WEB","url":"https://github.com/Chainlit/chainlit/blob/2.12.0/docs/security-advisory-2026-mcp.md#spl-2026-001--command-injection-via-mcp-stdio"},{"type":"WEB","url":"https://github.com/Chainlit/chainlit/commit/0565fd0eccb915fce159929598b053ed79f6e0c9"},{"type":"WEB","url":"https://github.com/Chainlit/chainlit/releases/tag/2.12.0"},{"type":"WEB","url":"https://github.com/Chainlit/chainlit/security/advisories/GHSA-w3fx-mc44-mf6j"},{"type":"WEB","url":"https://github.com/Chainlit/chainlit/security/advisories/GHSA-w3fx-mc44-mf6j"}],"provenance":{"sources":["OSV.dev","NVD","FIRST.org (EPSS)"],"lastVerified":"2026-08-25T20:16:55.720"}}