Medium severity · published Aug 20, 2026
CVE-2026-73259
Mongoose: Reflected XSS via decoded URI in directory listing render
5.4
CVSS
0.4%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
Required
Confidentiality
Low
Integrity
Low
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 35% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
MO
mongoose · cesanta
< 7.22 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-73259
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-73259
Patch
https://github.com/cesanta/mongoose/commit/a9df523f76f43a38bd53b4232b9cfd4c16869e71
Issue Tracking
https://github.com/cesanta/mongoose/pull/3611
Release Notes
https://github.com/cesanta/mongoose/releases/tag/7.22
Exploit
https://github.com/cesanta/mongoose/security/advisories/GHSA-9cwm-487w-h25w
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