Summary
A vulnerability in mcp-remote versions 0.1.16 through 0.1.38 involves insufficient validation of input passed to open() functions. A remote attacker may be able to influence this input to execute arbitrary code, with risk depending on how the affected component is exposed and what privileges it has.
Affected context
The issue occurs in mcp-remote deployments within the affected version range where remotely influenced data reaches an open() call without adequate validation or restriction. Risk may increase when the component accepts untrusted remote requests, can access sensitive local or network resources, or runs with elevated permissions.
Exploit preconditions
- Attack surface: A remotely reachable mcp-remote interface or service path that influences an
open()operation - Required access: Ability to send or control input processed by the affected component; authentication requirements depend on deployment configuration
- Trigger point: Processing attacker-influenced input by an
open()function - Why exploitation is possible: Input validation and resource restrictions may be insufficient, allowing crafted values to reach a sensitive file or resource operation and potentially participate in code execution
Why this happens
The underlying bug is improper validation of externally influenced input before it is used by a sensitive file or resource-opening operation. When an application treats such input as trusted, an attacker may manipulate the operation's target or behavior in ways the program does not safely constrain. This maps primarily to CWE-20: Improper Input Validation and may also involve CWE-94: Improper Control of Generation of Code and CWE-918: Server-Side Request Forgery where the affected data can influence executable behavior or network resource access.
Potential impact
- An attacker may execute arbitrary code in the mcp-remote process context
- Sensitive local files or environment data could be exposed
- Internal network services could be accessed from the affected runtime
- Application integrity, credentials, or downstream systems could be compromised
- Impact could extend to connected tools or services if the process has excessive privileges
General mitigation guidance
Mitigation generally focuses on reducing trust in externally supplied values and separating resource selection from executable behavior.
Common defensive patterns include:
- Validating inputs against strict allowlists for permitted paths, schemes, formats, and resources
- Avoiding dynamic interpretation of input as code or executable configuration
- Restricting file and network access to approved locations and destinations
- Applying safe-by-default parser and resource-opening APIs
- Running the component with least-privilege filesystem, network, and process permissions
- Isolating remote-facing functionality from sensitive hosts and internal services
- Enforcing authentication, authorization, and request-boundary validation before resource operations
How teams detect issues like this
Organizations can look for this class of issue through:
- Static analysis rules identifying attacker-controlled data flowing into
open()or equivalent resource APIs - Code review checks for dynamic path construction, unrestricted schemes, and input-dependent execution paths
- Tests that verify rejection of unexpected paths, protocols, encodings, and resource identifiers
- Runtime monitoring of unusual child-process creation, file access, and outbound connections
- Policy enforcement that restricts filesystem and network access for remote-facing services
- Automated security review tools that flag CWE-20, CWE-94, and CWE-918 data-flow patterns
