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CVE-2026-19484— @fastify/busboy vulnerable to Denial of Service via oversized multipart boundary

Quick assessment

Affected
@fastify/busboy @fastify/busboy
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Fastify busboy是Fastify组织的一款处理Web表单数据的中间件。 Fastify busboy 3.1.0版本至3.2.0版本存在安全漏洞，该漏洞源于multipart请求边界处理不当，可能导致远程未认证攻击者通过发送特制边界的multipart请求使Node.js事件循环停滞，造成拒绝服务。

CVSS 7.5 · High EPSS 0.61% · P48

Possible ATT&CK Techniques 1 AI

T1499 · Endpoint Denial of Service

Affected Version Matrix 2

VendorProduct Version RangeStatus
@fastify/busboy @fastify/busboy 3.1.0< 3.2.1 affected
3.2.1 unaffected
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I. Basic Information for CVE-2026-19484

Vulnerability Information
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Vulnerability Title
@fastify/busboy vulnerable to Denial of Service via oversized multipart boundary
Source: CVE Program / CVE List V5
Vulnerability Description
@fastify/busboy is a multipart form-data parser. In versions 3.1.0 through 3.2.0, a remote unauthenticated attacker can stall the Node.js event loop by sending a multipart request whose boundary is crafted to a specific length. The vendored streaming search stores its skip table in a fixed 256 entry byte array, and a boundary of exactly 252 bytes makes the search needle 256 bytes, which truncates the default skip distance to zero and turns the search into a CPU bound loop on a small body. A single small request can keep one core busy and deny service to other requests handled by the same process. The issue is fixed in @fastify/busboy 3.2.1, which widens the skip table so the skip distance is preserved. Users should upgrade to 3.2.1.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
不可达退出条件的循环(无限循环)
Source: CVE Program / CVE List V5
Vulnerability Title
Fastify busboy 处理逻辑错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Fastify busboy是Fastify组织的一款处理Web表单数据的中间件。 Fastify busboy 3.1.0版本至3.2.0版本存在安全漏洞，该漏洞源于multipart请求边界处理不当，可能导致远程未认证攻击者通过发送特制边界的multipart请求使Node.js事件循环停滞，造成拒绝服务。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
@fastify/busboy @fastify/busboy 3.1.0 ~ 3.2.1 -

II. Public POCs for CVE-2026-19484

# POC Description Source Link Shenlong Link
AI-Generated POC Verified env Premium
Qwen3.6-35B-A3B · 5455 chars
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Vulnerability reproduction recording (real sandbox build + trigger, exclusive)
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III. Intelligence Information for CVE-2026-19484

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Vendor Advisories for CVE-2026-19484 (1)

IV. Related Vulnerabilities

Same product: @fastify/busboy
Same vendor: @fastify/busboy
Same weakness: CWE-835

V. Comments for CVE-2026-19484

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