CVE-2026-53710 MCP Context Forge: RestrictedPython sandbox bypass via getattr builtin in python_sandbox_server
Attackers can execute arbitrary OS commands by bypassing the Python sandbox via runtime dunder traversal in the MCP Context Forge server.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-53710?
CVE-2026-53710 is a critical code injection vulnerability in IBM mcp-context-forge, published on 15 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
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.
Which versions are affected by CVE-2026-53710?
3 open source packages ship an affected version, including mcp-contextforge-gateway.
| Package | Affected | Fixed in |
|---|---|---|
mcp-contextforge-gateway PyPI | All versions | 1.0.2 |
mcp-contextforge-gateway PyPI | All versions | 1.0.2 |
mcp-contextforge-gateway PyPI | All versions | 1.0.2 |
How do I fix CVE-2026-53710?
Upgrade mcp-contextforge-gateway to 1.0.2 or later.
Upgrade, and never evaluate templates, expressions or code built from user input. More about Code injection.
Is CVE-2026-53710 being exploited?
There is no known exploitation of CVE-2026-53710 in the wild and no public exploit code.
Sources
Also known as GHSA-xm98-3vcf-fph7, PYSEC-2026-3862.