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CVE-2026-73258— Mongoose: Multipart boundary/header scan logic error in mg_http_next_multipart

Quick assessment

Affected
cesanta mongoose
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.

Cesanta Mongoose是爱尔兰Cesanta公司开源的一个嵌入式Web服务器。 Cesanta Mongoose 7.22之前版本存在处理逻辑错误漏洞，该漏洞源于mg_http_next_multipart()函数处理multipart输入时比较循环条件错误，可能导致截断头部、文件名或边界，从而在收到误导性Content-Type值后接受危险内容。

CVSS 6.5 · Medium EPSS 0.46% · P38

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 1

VendorProduct Version RangeStatus
cesanta mongoose < 7.22 affected
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I. Basic Information for CVE-2026-73258

Vulnerability Information
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Vulnerability Title
Mongoose: Multipart boundary/header scan logic error in mg_http_next_multipart
Source: CVE Program / CVE List V5
Vulnerability Description
Mongoose is an embedded web server and network library. Prior to 7.22, a remote attacker can place a lone carriage return or line feed in multipart input processed by mg_http_next_multipart() in src/http.c. The loops comparing s[b] and s[b + 1], and s[h2] and s[h2 + 1], use an incorrect AND condition and stop when either character resembles part of a CRLF terminator. This truncates headers, filenames, or boundaries and can cause an application to accept dangerous content after seeing a misleading Content-Type value. This issue is fixed in version 7.22.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
不充分的比较
Source: CVE Program / CVE List V5
Vulnerability Title
Cesanta Mongoose 处理逻辑错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Cesanta Mongoose是爱尔兰Cesanta公司开源的一个嵌入式Web服务器。 Cesanta Mongoose 7.22之前版本存在处理逻辑错误漏洞，该漏洞源于mg_http_next_multipart()函数处理multipart输入时比较循环条件错误，可能导致截断头部、文件名或边界，从而在收到误导性Content-Type值后接受危险内容。
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
cesanta mongoose < 7.22 -

II. Public POCs for CVE-2026-73258

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III. Intelligence Information for CVE-2026-73258

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Patches & Fixes for CVE-2026-73258 (1)

Vendor Advisories for CVE-2026-73258 (1)

Vendor Pages for CVE-2026-73258 (1)

Same Patch Batch · cesanta · 2026-08-20 · 8 CVEs total

CVE-2026-73251 9.3 CRITICAL Mongoose Built-in TLS: CA-bundle certificate chain accepted without any signature verifica
CVE-2026-73257 9.1 CRITICAL Mongoose: Content-Length + Transfer-Encoding coexistence enables request smuggling
CVE-2026-73256 9.1 CRITICAL Mongoose: HTTP/1.0 detection off-by-one enables request smuggling via chunked TE
CVE-2026-73253 9.1 CRITICAL Mongoose: TLS Hostname Verification Bypass via Overly Permissive Wildcard Matching
CVE-2026-73255 6.5 MEDIUM Mongoose: Path traversal in SSI #include directives enables arbitrary file read
CVE-2026-73254 5.4 MEDIUM Mongoose: Stored XSS via unescaped filenames in directory listing
CVE-2026-73259 5.4 MEDIUM Mongoose: Reflected XSS via decoded URI in directory listing render

IV. Related Vulnerabilities

Same product: mongoose
Same vendor: cesanta
Same weakness: CWE-697

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