XSS in Cesanta Mongoose
CVE-2026-73259
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.
Vulnerability class: XSS (Cross-Site Scripting)
CVSS v3 metric
CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N.
Affected products
- Cesanta Mongoose — versions < 7.22
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM)
- security-advisories@github.com (x_refsource_MISC)
- security-advisories@github.com (x_refsource_MISC)
- security-advisories@github.com (x_refsource_MISC)
Frequently asked questions
- What is CVE-2026-73259?
- CVE-2026-73259 is a medium-severity vulnerability in Cesanta Mongoose, classified under Cross-site Scripting. CVSS score: 5.4/10. Published 2026-08-20.
- How severe is CVE-2026-73259?
- Medium severity. CVSS v3 base score is 5.4 out of 10.