Cesanta Mongoose up to 7.21 Ssi src/ssi.c mg_ssi path traversal

Summaryinfo

A vulnerability marked as problematic has been reported in Cesanta Mongoose up to 7.21. This vulnerability affects the function mg_ssi of the file src/ssi.c of the component Ssi. The manipulation leads to path traversal. This vulnerability is listed as CVE-2026-73255. The attack may be initiated remotely. There is no available exploit.

Detailsinfo

A vulnerability was found in Cesanta Mongoose up to 7.21. It has been rated as problematic. This issue affects the function mg_ssi of the file src/ssi.c of the component Ssi. The manipulation with an unknown input leads to a path traversal vulnerability. Using CWE to declare the problem leads to CWE-22. The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory. Impacted is confidentiality. The summary by CVE is:

Mongoose is an embedded web server and network library. Prior to 7.22, an attacker who can control an SSI-enabled file can place directory traversal sequences in an #include file or #include virtual directive. The mg_ssi() function in src/ssi.c concatenates the directive argument into a filesystem path without calling mg_path_is_sane(), allowing an MG_ENABLE_SSI deployment with ssi_pattern configured to disclose files readable by the Mongoose process. This issue is fixed in version 7.22.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-73255 since 08/11/2026. The exploitation is known to be easy. The attack may be initiated remotely. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1006 according to MITRE ATT&CK.

Upgrading to version 7.22 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at CNNVD (CNNVD-2026-99105302). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

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/

CPE 2.3info

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CPE 2.2info

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Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

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