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CVE-2026-66729— facil.io 0.6.0 - 0.7.6 Integer Underflow DoS via Multipart MIME Body Parser

Quick assessment

Affected
boazsegev facil.io
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.

facil.io 0.7.6 及之前版本在 multipart MIME 体解析器中存在整数下溢漏洞，允许未经身份验证的远程攻击者通过发送包含空字段名的构造的 Content-Disposition 头信息来导致服务器进程崩溃。攻击者可触发 http_mime_parser.h 中的 uint32_t 整数回绕（wraparound），导致在名称指针之后发生越界内存读取，从而引发总线错误（bus fault），使得处理该请求的工作线程在接收到单个 POST 请求后崩溃。

CVSS 7.5 · High EPSS 0.78% · P54

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 1

VendorProduct Version RangeStatus
boazsegev facil.io 0.6.0≤ 0.7.6 affected
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I. Basic Information for CVE-2026-66729

Vulnerability Information
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Vulnerability Title
facil.io 0.6.0 - 0.7.6 Integer Underflow DoS via Multipart MIME Body Parser
Source: CVE Program / CVE List V5
Vulnerability Description
facil.io 0.6.0 through 0.7.6 contains an integer underflow vulnerability in the multipart MIME body parser that allows unauthenticated remote attackers to crash the server process by sending a crafted Content-Disposition header with an empty field name. Attackers can trigger a uint32_t wraparound in http_mime_parser.h causing an out-of-bounds memory read past the name pointer, resulting in a bus fault that crashes the handling worker with a single POST request.
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
跨界内存读
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
boazsegev facil.io 0.6.0 ~ 0.7.6 -

II. Public POCs for CVE-2026-66729

# POC Description Source Link Shenlong Link
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Qwen3.6-35B-A3B · 7129 chars
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III. Intelligence Information for CVE-2026-66729

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Vendor Advisories for CVE-2026-66729 (1)

Proof of Concept for CVE-2026-66729 (1)

Security Blog Posts for CVE-2026-66729 (1)

Same Patch Batch · boazsegev · 2026-07-27 · 3 CVEs total

CVE-2026-66730 7.5 HIGH facil.io 0.6.0 - 0.7.6 Infinite Loop DoS via Multipart MIME Body Parser
CVE-2026-66731 7.5 HIGH facil.io 0.7.5 - 0.7.6 HTTP/1.1 Chunked Transfer Encoding Parser Crash DoS

IV. Related Vulnerabilities

Same product: facil.io
Same vendor: boazsegev
Same weakness: CWE-125

V. Comments for CVE-2026-66729

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