Cesanta Mongoose up to 7.21 src/http.c mg_http_next_multipart crlf injection

Summaryinfo

A vulnerability classified as critical has been found in Cesanta Mongoose up to 7.21. Impacted is the function mg_http_next_multipart of the file src/http.c. This manipulation causes crlf injection. This vulnerability is registered as CVE-2026-73258. Remote exploitation of the attack is possible. No exploit is available.

Detailsinfo

A vulnerability classified as critical was found in Cesanta Mongoose up to 7.21. Affected by this vulnerability is the function mg_http_next_multipart of the file src/http.c. The manipulation with an unknown input leads to a crlf injection vulnerability. The CWE definition for the vulnerability is CWE-93. The product uses CRLF (carriage return line feeds) as a special element, e.g. to separate lines or records, but it does not neutralize or incorrectly neutralizes CRLF sequences from inputs. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

Mongoose is an embedded web server and network library. Prior to 7.22, a remote attacker can place a lone carriage return or line feed in multipart input processed by mg_http_next_multipart() in src/http.c. The loops comparing s[b] and s[b + 1], and s[h2] and s[h2 + 1], use an incorrect AND condition and stop when either character resembles part of a CRLF terminator. This truncates headers, filenames, or boundaries and can cause an application to accept dangerous content after seeing a misleading Content-Type value. This issue is fixed in version 7.22.

The advisory is shared at github.com. This vulnerability is known as CVE-2026-73258 since 08/11/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Technical details are known, but no exploit is available.

The vulnerability scanner Nessus provides a plugin with the ID 338659 (Linux Distros Unpatched Vulnerability : CVE-2026-73258), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 7.22 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at Tenable (338659). If you want to get the best quality for vulnerability data then you always have to consider VulDB.

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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