Chainlit: Command injection via MCP stdio transport allows unauthenticated remote code execution (CVE-2026-45018) | HOL Guard CVE

Unknown severity · Source severity not reportedCVE-2026-45018

Chainlit: Command injection via MCP stdio transport allows unauthenticated remote code execution

Answer in brief

CVE-2026-45018 records a Unknown severity vulnerability in Chainlit: Command injection via MCP stdio transport allows unauthenticated remote code execution. The current sources do not mark it as known exploited. The current feed maps Chainlit/chainlit (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Aug 25, 2026Updated Aug 25, 2026Source checked Aug 25, 2026First seen by HOL Aug 25, 2026Material review Aug 25, 2026

Upstream Advisory

Key facts

Risk: Unknown severitySource severity not reported
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Not reported

Why this deserves its current priority

A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps Chainlit/chainlit (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
Chainlit/chainlitgeneric	>= 2.4.0rc0, < 2.12.0	Not reported

Recommended response

Check inventory. Check lockfiles and deployed manifests for Chainlit/chainlit.
Review the reported fix. Monitor this advisory for an available fix and review any installs of the affected package.

Evidence timeline and material changes

Published upstream
Aug 25, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Aug 25, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Aug 25, 2026

Sources and claim methodology

Upstream source 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.

Quoted source text, attributed separately from HOL analysis.