Cesanta Mongoose up to 7.21 src/http.c printdirentry cross site scripting

Summaryinfo

A vulnerability, which was classified as problematic, was found in Cesanta Mongoose up to 7.21. This affects the function printdirentry of the file src/http.c. Executing a manipulation can lead to cross site scripting. This vulnerability appears as CVE-2026-73254. The attack may be performed from remote. There is no available exploit.

Detailsinfo

A vulnerability has been found in Cesanta Mongoose up to 7.21 and classified as problematic. This vulnerability affects the function printdirentry of the file src/http.c. The manipulation with an unknown input leads to a cross site scripting vulnerability. The CWE definition for the vulnerability is CWE-79. The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. As an impact it is known to affect integrity. CVE summarizes:

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.

The advisory is shared for download at github.com. This vulnerability was named CVE-2026-73254 since 08/11/2026. The exploitation appears to be easy. The attack can be initiated remotely. Successful exploitation requires user interaction by the victim. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1059.007.

Upgrading to version 7.22 eliminates this vulnerability.

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Productinfo

Vendor

• Cesanta

Name

• Mongoose

Version

• 7.0
• 7.1
• 7.2
• 7.3
• 7.4
• 7.5
• 7.6
• 7.7
• 7.8
• 7.9
• 7.10
• 7.11
• 7.12
• 7.13
• 7.14
• 7.15
• 7.16
• 7.17
• 7.18
• 7.19
• 7.20
• 7.21

License

• open-source

Website

• Product: https://github.com/cesanta/mongoose/

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