# CVE-2026-11918: IBM ContextForge MCP Gateway protection bypass in nested payload inspection

Source: https://junglewise.ai/threats/cve-2026-11918-ibm-contextforge-mcp-gateway-protection-bypass-in-nested-payload  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-15. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-11918 · Severity: medium · CVSS 5.4 · Published 2026-09-15

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.

Technologies: [IBM ContextForge MCP Gateway](https://junglewise.ai/threats/technologies/contextforge-mcp-gateway). Vendors: [IBM](https://junglewise.ai/threats/vendors/ibm).

## Quick answers

**Is CVE-2026-11918 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-11918 being exploited in the wild.

**How severe is CVE-2026-11918?** Medium severity, with a CVSS score of 5.4, published 15 September 2026.

**Which products and versions are affected?** IBM ContextForge MCP Gateway <=1.0.4.

**Is there a fix for CVE-2026-11918?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-11918 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-11918?** Check whether you run IBM ContextForge MCP Gateway at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## 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

## References

- [https://www.ibm.com/support/pages/node/7285720](https://www.ibm.com/support/pages/node/7285720)

## Related threats

- [IBM ContextForge MCP Gateway denial of service in tool slug normalization](https://junglewise.ai/threats/cve-2026-18484-ibm-contextforge-mcp-gateway-1-0-0-through-1-0-11-could-allow-a)
- [IBM ContextForge MCP Gateway server-side request forgery in OAuth registration](https://junglewise.ai/threats/cve-2026-8355-ibm-contextforge-mcp-gateway-0-1-0-through-1-0-5-is-vulnerable-to)
- [IBM ContextForge MCP Gateway path traversal in Admin API](https://junglewise.ai/threats/cve-2026-77825-ibm-contextforge-mcp-gateway-1-0-0-through-1-0-8-was-vulnerable)
- [IBM ContextForge MCP Gateway default credentials auth bypass](https://junglewise.ai/threats/cve-2026-78573-ibm-contextforge-mcp-gateway-default-credentials-auth-bypass)
- [IBM ContextForge MCP Gateway jq filter injection credential disclosure](https://junglewise.ai/threats/cve-2026-18486-ibm-contextforge-mcp-gateway-jq-filter-injection-credential)