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CVE-2026-88257— beam_mcp: nested tool argument constraints advertised but not enforced

Quick assessment

Affected
ScriptKittyOS beam_mcp
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

BeamMCP.Schema 中存在不正确的输入验证漏洞。在 ScriptKittyOS 的 beam_mcp 中，该漏洞允许 MCP 客户端使用违反服务器所声明输入架构参数的值，来调用工具的分发函数。BeamMCP.Schema.validate/2 仅对顶层参数对象检查了类型（type）、必需字段（required）、额外属性（additionalProperties）、枚举值（enum）以及数值范围限制。然而，工具通过 tools/list 声明的那些嵌套对象内部的约束条件以及数组项的约束（如 items、m

CVSS 5.3 · Medium

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application
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I. Basic Information for CVE-2026-88257

Vulnerability Information
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Vulnerability Title
beam_mcp: nested tool argument constraints advertised but not enforced
Source: CVE Program / CVE List V5
Vulnerability Description
Improper Input Validation vulnerability in BeamMCP.Schema in ScriptKittyOS beam_mcp allows an MCP client to reach a tool's dispatch function with arguments that violate the input schema the server advertised. BeamMCP.Schema.validate/2 checked type, required, additionalProperties, enum and numeric bounds on the top-level arguments object only. Constraints inside nested objects and on array items (items, minItems, maxItems, minLength, maxLength, pattern, nested required, enum and additionalProperties: false) were advertised by tools/list and never checked at tools/call or prompts/get, and keywords outside the enforced subset (oneOf, anyOf, $ref) were advertised and ignored. A host whose dispatch code relies on the schema it declared receives values the schema forbids, such as an out-of-range number or an undeclared key inside a nested object. What the host does with such a value decides the impact. This issue affects beam_mcp: from 0.1.0 before 0.10.1.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
输入验证不恰当
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
ScriptKittyOS beam_mcp 0.1.0 ~ 0.10.1 cpe:2.3:a:scriptkittyos:beam_mcp:*:*:*:*:*:*:*:*
ScriptKittyOS beam_mcp 083838eb8e17fe5f6fcaf761bdbe203110288b0b ~ 289dbdbad641943b29a3b8d1eb36506cc8cec10a cpe:2.3:a:scriptkittyos:beam_mcp:*:*:*:*:*:*:*:*

II. Public POCs for CVE-2026-88257

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III. Intelligence Information for CVE-2026-88257

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Other References for CVE-2026-88257 (5)

IV. Related Vulnerabilities

Same product: beam_mcp
Same vendor: ScriptKittyOS
Same weakness: CWE-20

V. Comments for CVE-2026-88257

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