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CVE-2026-6985— Cesanta Mongoose TCP Option net_builtin.c handle_opt infinite loop

Quick assessment

Affected
Cesanta Mongoose
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Cesanta Mongoose是爱尔兰Cesanta公司的一套嵌入式服务器库，它包括TCP、HTTP客户端和服务器、WenSocket客户端和服务器等功能。 Cesanta Mongoose 7.20及之前版本存在安全漏洞，该漏洞源于组件TCP Option Handler中文件/src/net_builtin.c的函数handle_opt对参数optlen操作不当，可能导致无限循环。

CVSS 5.3 · Medium EPSS 0.92% · P59
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I. Basic Information for CVE-2026-6985

Vulnerability Information
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Vulnerability Title
Cesanta Mongoose TCP Option net_builtin.c handle_opt infinite loop
Source: CVE Program / CVE List V5
Vulnerability Description
A weakness has been identified in Cesanta Mongoose up to 7.20. This vulnerability affects the function handle_opt of the file /src/net_builtin.c of the component TCP Option Handler. This manipulation of the argument optlen causes infinite loop. The attack is possible to be carried out remotely. The exploit has been made available to the public and could be used for attacks. Upgrading to version 7.21 is able to resolve this issue. Upgrading the affected component is advised. VulDB has contacted the vendor early and they confirmed quickly, that this issue got fixed already.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Source: CVE Program / CVE List V5
Vulnerability Type
不可达退出条件的循环(无限循环)
Source: CVE Program / CVE List V5
Vulnerability Title
Cesanta Mongoose 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Cesanta Mongoose是爱尔兰Cesanta公司的一套嵌入式服务器库，它包括TCP、HTTP客户端和服务器、WenSocket客户端和服务器等功能。 Cesanta Mongoose 7.20及之前版本存在安全漏洞，该漏洞源于组件TCP Option Handler中文件/src/net_builtin.c的函数handle_opt对参数optlen操作不当，可能导致无限循环。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Cesanta Mongoose 7.0 cpe:2.3:a:cesanta:mongoose:*:*:*:*:*:*:*:*

II. Public POCs for CVE-2026-6985

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III. Intelligence Information for CVE-2026-6985

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News Coverage for CVE-2026-6985 (1)

IV. Related Vulnerabilities

Same product: Mongoose
Same vendor: Cesanta
Same weakness: CWE-835

V. Comments for CVE-2026-6985

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