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CVE-2026-73259— Mongoose: Reflected XSS via decoded URI in directory listing render

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.

Mongoose 是一个嵌入式 Web 服务器和网络库。在 7.22 版本之前，远程攻击者可以向启用了 MG_ENABLE_DIRLIST 选项的部署发送构造的百分比编码请求路径，并诱使用户访问该路径。在 src/http.c 中，mg_http_serve_dir() 和 listdir() 函数将解码后的请求 URI 直接放入 HTML 的 title 和 h1 元素中，而未进行 HTML 实体编码。这会导致在 Mongoose 原始域上下文中执行反射型跨站脚本（XSS），从而可能暴露用户的会话数据或冒充受害者

CVSS 5.4 · Medium EPSS 0.23% · P15

Affected Version Matrix 1

VendorProduct Version RangeStatus
cesanta mongoose < 7.22 affected
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I. Basic Information for CVE-2026-73259

Vulnerability Information
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Vulnerability Title
Mongoose: Reflected XSS via decoded URI in directory listing render
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 send a crafted percent-encoded request path to a deployment using MG_ENABLE_DIRLIST and persuade a user to visit it. The mg_http_serve_dir() and listdir() path in src/http.c places the decoded request URI into the title and h1 elements without HTML entity encoding. The resulting reflected cross-site scripting executes in the Mongoose origin and can expose session data or perform actions as the victim. 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:R/S:U/C:L/I:L/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
在Web页面生成时对输入的转义处理不恰当(跨站脚本)
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
cesanta mongoose < 7.22 -

II. Public POCs for CVE-2026-73259

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III. Intelligence Information for CVE-2026-73259

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Patches & Fixes for CVE-2026-73259 (1)

Vendor Advisories for CVE-2026-73259 (1)

Vendor Pages for CVE-2026-73259 (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-2026-73258 6.5 MEDIUM Mongoose: Multipart boundary/header scan logic error in mg_http_next_multipart
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

IV. Related Vulnerabilities

Same product: mongoose
Same vendor: cesanta
Same weakness: CWE-79

V. Comments for CVE-2026-73259

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