Vulnerability · Published Sep 15, 2026 · Assigned by GitHub_M
CVE-2026-53710MCP Context Forge: RestrictedPython sandbox bypass via getattr builtin in python_sandbox_server
Critical 10.0
In plain English
A critical-severity code injection in mcp-context-forge from IBM. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 1.1% (higher than 67% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
MCP Context Forge is an AI gateway, registry, and proxy for MCP, A2A, REST, and gRPC APIs. Prior to 1.0.2, the python_sandbox_server in mcp-servers/python/python_sandbox_server/src/python_sandbox_server/server_fastmcp.py exposes raw getattr through safe_builtins, omits a required _getattr_ guard, and relies on validate_code checks for literal dangerous dunder strings. An attacker can construct dunder names at runtime, traverse the Python class hierarchy, reach subprocess.Popen, and execute OS commands with the server process privileges through the execute_code MCP tool. The HTTP/SSE transport can expose this tool without authentication, while stdio-only deployments have reduced network reachability. The issue affects the python_sandbox_server subproject and does not directly affect the core Context Forge gateway or proxy components. This issue is fixed in version 1.0.2.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| PyPI | mcp-contextforge-gateway | 1.0.2 | GHSA-xm98-3vcf-fph7 |
| PyPI | mcp-contextforge-gateway | 1.0.2 | PYSEC-2026-3862 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| IBM | mcp-context-forge | < 1.0.2 |
Weakness: CWE-94, CWE-693 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H