XSS in Cesanta Mongoose
CVE-2026-73254
Mongoose is an embedded web server and network library. Prior to 7.22, an attacker who can create a file with an HTML payload in its name can trigger stored cross-site scripting when a user browses a directory served with MG_ENABLE_DIRLIST. The printdirentry() path called by listdir() in src/http.c URL-encodes the href but inserts the raw filesystem filename into the HTML link text. The browser executes the injected markup in the Mongoose origin, which can expose session data or permit actions as the victim. This issue is fixed in version 7.22.
Vulnerability class: XSS (Cross-Site Scripting)
Published · last modified .
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.
EPSS exploit prediction
EPSS: 0.003 (25.6th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 26th percentile — 25.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.003 · change: +0.002
Affected products
- Cesanta Mongoose — versions < 7.22
Weakness classification (CWE)
References
- github.com/cesanta/mongoose/security/advisories/GHSA-5g6j-m3pv-4f7g (Exploit, Vendor Advisory)
- github.com/cesanta/mongoose/pull/3611 (Patch, Issue Tracking)
- github.com/cesanta/mongoose/commit/a9df523f76f43a38bd53b4232b9cfd4c16869e71 (Patch)
- github.com/cesanta/mongoose/releases/tag/7.22 (Release Notes)
Frequently asked questions
- What is CVE-2026-73254?
- CVE-2026-73254 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-2026-73254?
- Medium severity. CVSS v3 base score is 5.4 out of 10.