Executive brief
IBM ContextForge MCP Gateway is a security component that inspects and validates message payloads in cloud environments. An authenticated attacker can bypass its protection mechanisms by crafting deeply nested payloads that are not fully inspected, potentially allowing malicious content to pass through security controls.
Technical details
The vulnerability is a protection mechanism bypass stemming from incomplete recursive inspection of nested payload content in IBM ContextForge MCP Gateway versions up to v1.0.4. An authenticated attacker can exploit this flaw by crafting payloads with nested structures that the gateway's validation logic fails to fully traverse, allowing protected content to bypass security checks. The attack requires valid authentication credentials to access the gateway. Exploitation could permit delivery of malicious payloads that would normally be blocked, potentially compromising downstream systems. IBM has assigned CVE-2026-11918 to this issue.
Affected products
- IBM ContextForge MCP Gateway <=1.0.4
Timeline
- 2026-09-15: disclosed