Critical severity · published Sep 15, 2026
CVE-2026-53710
MCP Context Forge: RestrictedPython sandbox bypass via getattr builtin in python_sandbox_server
10.0
CVSS
1.1%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Changed
Exploitation
Is it being used?
Exploit prediction (EPSS)1.1% · higher than 66% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
MC
mcp-context-forge · IBM
< 1.0.2 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-53710
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-53710
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/security/advisories/GHSA-xm98-3vcf-fph7
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