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ContextForge MCP Gateway CVE-2026-11918

| EUVDEUVD-2026-78898 MEDIUM
Incomplete List of Disallowed Inputs (CWE-184)
2026-09-15 ibm GHSA-x4xw-xv9j-3c3q
5.4
CVSS 3.1 · NVD
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Severity by source

Vendor (ibm) PRIMARY
MEDIUM
qualitative
NVD
5.4 MEDIUM
AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
vuln.today AI
5.4 MEDIUM

Network-reachable, low complexity, but requires an authenticated gateway account (PR:L); only low C/I impact with no availability loss.

3.1 AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
4.0 AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N

Primary rating from Vendor (ibm).

CVSS VectorNVD

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
Low
Availability
None

Lifecycle Timeline

1
Analysis Generated
Sep 15, 2026 - 18:08 vuln.today

DescriptionNVD

IBM ContextForge MCP Gateway <= v1.0.4 IBM mcp-context-forge could allow an authenticated user to bypass protection mechanisms due to incomplete recursive inspection of nested payload content.

AnalysisAI

Authenticated users of IBM ContextForge MCP Gateway through v1.0.4 can bypass the gateway's payload protection mechanisms because its recursive content inspection does not fully traverse deeply nested or embedded payload structures. Successful abuse yields limited but real integrity and confidentiality impact (CVSS 5.4, AV:N/AC:L/PR:L/UI:N) by allowing disallowed content or instructions to pass through the filter that is meant to stop them, undermining the gateway's role as a security boundary between MCP clients and downstream tool servers. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Recon
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Delivery
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Exploit
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Install
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C2
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Execute
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Impact
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Vulnerability AssessmentAI

Exploitation Exploitation requires a valid authenticated account on the IBM ContextForge MCP Gateway (PR:L per the published CVSS vector) and the ability to submit payloads that the gateway forwards to a downstream MCP server - i.e., the gateway's payload inspection or content-filtering path must be in use, which is its default function. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The CVSS 3.1 vector (AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N, 5.4) describes a network-reachable, low-complexity attack that nonetheless requires a valid authenticated account and produces only low confidentiality and integrity impact with no availability effect - a moderate, not catastrophic, profile. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario Full exploit scenario with step-by-step reproduction available after sign-in.
Remediation Upgrade IBM ContextForge MCP Gateway beyond v1.0.4 to the fixed release described in the IBM advisory at https://www.ibm.com/support/pages/node/7285720 - patch availability is vendor-confirmed but the exact fixed version string is not specified in the supplied data, so verify it on the support page before scheduling. … Detailed patch versions, workarounds, and compensating controls in full report.

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CVE-2026-11918 vulnerability details – vuln.today

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