What’s Vulnerable › Vulnerabilities

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

• Severity: medium (CVSS 5.4 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-08-20 · updated 2026-10-18
• Weakness: CWE-79

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.

Affected products

• Cesanta Mongoose: before 7.22 — fixed in 7.22

How to fix

Upgrade to a fixed version: Cesanta Mongoose 7.22. Check the vendor advisory for mitigations.

References

• https://github.com/cesanta/mongoose/commit/a9df523f76f43a38bd53b4232b9cfd4c16869e71
• https://github.com/cesanta/mongoose/pull/3611
• https://github.com/cesanta/mongoose/releases/tag/7.22
• https://github.com/cesanta/mongoose/security/advisories/GHSA-9cwm-487w-h25w
• https://github.com/cesanta/mongoose/security/advisories/GHSA-9cwm-487w-h25w

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