CVE-2026-88257Network attack vectorHinoki check available

Schema bypass via unchecked nested argument constraints

Published Oct 8, 2026 · Updated Oct 8, 2026

Input validation in ScriptKittyOS BeamMCP before 0.10.1 allows attackers to bypass tool schemas through crafted MCP arguments. BeamMCP.Schema.validate/2 checks only top-level constraints, leaving nested objects, array items, string constraints, and unsupported schema keywords unchecked before dispatch. Exploitation requires access to the host's MCP interface and a schema using ignored constraints; consequences depend on how the host processes the forbidden values.

CVSS severity5.3
Medium
EPSS probability0.27%
Next 30 days · Oct 19, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Input validation in ScriptKittyOS BeamMCP before 0.10.1 allows attackers to bypass tool schemas through crafted MCP arguments. BeamMCP.Schema.validate/2 checks only top-level constraints, leaving nested objects, array items, string constraints, and unsupported schema keywords unchecked before dispatch. Exploitation requires access to the host's MCP interface and a schema using ignored constraints; consequences depend on how the host processes the forbidden values.

The record

CVE
CVE-2026-88257
Published
Oct 8, 2026
Updated
Oct 8, 2026
Vendor
ScriptKittyOS
Product
BeamMCP
Classifications
CWE-1284, CWE-20
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Oct 8, 2026CVE publishedPublication date reported by the CVE source.
  2. Oct 8, 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=0.1.0 <0.10.1
  2. Affected versionversion=083838eb8e17fe5f6fcaf761bdbe203110288b0b <289dbdbad641943b29a3b8d1eb36506cc8cec10a

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

ScriptKittyOS · BeamMCPversion=0.1.0 <0.10.1; version=083838eb8e17fe5f6fcaf761bdbe203110288b0b <289dbdbad641943b29a3b8d1eb36506cc8cec10a

Published CVSS scores

5.3ScriptKittyOSCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA: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.

Activity data is delayed. The latest report is Sep 28, 2026.

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

No observations available

Sep 22, 2026Sep 28, 2026
Latest reporting daySep 28, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-1284Improper Validation of Specified Quantity in Input
CWE-20Improper Input Validation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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