Intel

AIKIDO-2026-524114

cesanta.mongoose is vulnerable to Cross-Site Scripting (XSS)

Cross-Site Scripting (XSS)CVE-2026-73259 Published Aug 13, 2026

54

Medium Risk

This Affects:

C++cesanta.mongoose
7.0.0 - 7.21.0
Fixed in 7.22.0
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TL;DR

When directory listing is enabled, the request path is URL-decoded and written into the listing page title and heading without HTML-entity encoding. A crafted link whose path contains markup causes that markup to execute in the browser of a user who follows it. This reflected cross-site scripting runs in the origin of the Mongoose server and needs no write access. The fix HTML-escapes the decoded path before rendering.

Who does this affect?

You are affected if you are using a version that falls within the vulnerable range and you serve directory listings with MG_ENABLE_DIRLIST enabled.

Background info

cesanta.mongoose is vulnerable to Cross-Site Scripting (XSS) in versions 7.0.0 - 7.21.0.

How to fix this

Upgrade the cesanta.mongoose library to the patch version.