CVE-2026-29791Network attack vector

Upstream request manipulation via unencoded MCP parameters

Published Mar 6, 2026 · Updated Mar 6, 2026

Improper input validation in agentgateway before 0.12.0 allows remote authenticated users to inject parameters into upstream requests. The MCP-to-OpenAPI converter forwards unencoded tool-call path, query, and header values, allowing crafted values to add parameters and headers. Exposure requires the MCP-to-OpenAPI feature and low-privileged access; successful requests can read or alter data handled by the upstream service.

CVSS severity4.9
Medium
EPSS probability0.14%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper input validation in agentgateway before 0.12.0 allows remote authenticated users to inject parameters into upstream requests. The MCP-to-OpenAPI converter forwards unencoded tool-call path, query, and header values, allowing crafted values to add parameters and headers. Exposure requires the MCP-to-OpenAPI feature and low-privileged access; successful requests can read or alter data handled by the upstream service.

The record

CVE
CVE-2026-29791
Published
Mar 6, 2026
Updated
Mar 6, 2026
Vendor
agentgateway
Product
agentgateway
Classifications
CWE-20, T1565.002
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 6, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 6, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 0.12.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

agentgateway · agentgatewayversion=< 0.12.0

Published CVSS scores

4.9GitHub, Inc.CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:L/A:N
6.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-20Improper Input Validation
T1565.002Transmitted Data Manipulation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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