# 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.

- **Severity:** Critical 10.0 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 15 Sep 2026
- **Updated:** 15 Sep 2026
- **Also known as:** GHSA-xm98-3vcf-fph7, PYSEC-2026-3862

## 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.

Weakness: CWE-94 (Improper Control of Generation of Code), CWE-693 (Protection Mechanism Failure)

## Which versions are affected by CVE-2026-53710?

3 open source packages ship an affected version, including mcp-contextforge-gateway.


| Package | Ecosystem | 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.

## Is CVE-2026-53710 being exploited?

There is no known exploitation of CVE-2026-53710 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-53710 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-53710 in the wild and no public exploit code.

Affected packages and fixed versions:
- mcp-contextforge-gateway (PyPI): affected all versions; fixed in 1.0.2
- mcp-contextforge-gateway (PyPI): affected all versions; fixed in 1.0.2
- mcp-contextforge-gateway (PyPI): affected all versions; fixed in 1.0.2

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-53710/ (Markdown: https://insights.sbomify.com/CVE-2026-53710/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-53710
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-53710
- OSV: https://osv.dev/vulnerability/CVE-2026-53710

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-53710/
Summaries are generated and may contain mistakes; the official description above is the record.