---
title: "CVE-2026-53710: mcp-contextforge-gateway has RestrictedPython sandbox bypass via getattr builtin in python_sandbox_server"
url: https://erroneo.us/security/cve/CVE-2026-53710/
description: "CVE-2026-53710 (mcp-contextforge-gateway (PyPI)): MCP Context Forge is an AI gateway, registry, and proxy for MCP, A2A, REST, and gRPC APIs. Prior to 1.0.2…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-09-15
date_modified: 2026-10-15
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-53710"
kev: false
cvss: 10
epss: 0.01141
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2026-53710: mcp-contextforge-gateway has RestrictedPython sandbox bypass via getattr builtin in python_sandbox_server

**Signal:** Critical and remotely reachable. No known exploitation yet, but it is network-reachable without credentials. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
- EPSS 1.1% , percentile 66: FIRST’s model estimates a 1.1% chance of exploitation activity in the next 30 days, higher than 66% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Only applies if your dependency tree includes mcp-contextforge-gateway (PyPI) <= 1.0.1, fixed in 1.0.2 . Check your lockfile, including transitive dependencies.

## What it is

MCP Context Forge is an AI gateway, registry, and proxy for MCP, A2A, REST, and gRPC APIs. Prior to 1.0.2, the pythonsandboxserver in mcp-servers/python/pythonsandboxserver/src/pythonsandboxserver/serverfastmcp.py exposes raw getattr through safebuiltins, omits a required getattr guard, and relies on validatecode 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 executecode MCP tool. The HTTP/SSE transport can expose this tool without authentication, while stdio-only deployments have reduced network reachability. The issue affects the pythonsandboxserver 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

- PyPI `mcp-contextforge-gateway` <= 1.0.1 → fixed: 1.0.2

## Affected products (CVE record)

- IBM mcp-context-forge: < 1.0.2

## Severity

- GitHub_M CVSS 3.1: 10 `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H`
- GitHub CVSS 3.1: 10.0 `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H`

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation none , automatable yes , technical impact total .
- FIRST EPSS (model of 2026-10-21): 1.14% probability of exploitation activity in the next 30 days; percentile 66.

## Sources

- [GitHub Advisory GHSA-xm98-3vcf-fph7](https://github.com/advisories/GHSA-xm98-3vcf-fph7)
- [CVE.org record CVE-2026-53710](https://www.cve.org/CVERecord?id=CVE-2026-53710)
- [NVD entry CVE-2026-53710](https://nvd.nist.gov/vuln/detail/CVE-2026-53710)
- [github.com](https://github.com/IBM/mcp-context-forge/security/advisories/GHSA-xm98-3vcf-fph7)
- [github.com](https://github.com/IBM/mcp-context-forge/commit/63a2900e6301b9c8a483a38d3737a1beb3a7ce89)
- [github.com](https://github.com/IBM/mcp-context-forge/releases/tag/v1.0.2)
- [github.com](https://github.com/IBM/mcp-context-forge/releases#release-v1.0.2)

---
Source page: https://erroneo.us/security/cve/CVE-2026-53710/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt