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CVE-2026-11404— Cesanta Mongoose Out-of-Bounds Read in MG_TLS_BUILTIN ClientHello Session ID Parsing

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公司开源的一个嵌入式Web服务器库。 Cesanta Mongoose 7.22之前版本存在缓冲区错误漏洞，该漏洞源于内置TLS服务器函数mg_tls_server_recv_hello()中存在越界读取，该函数使用攻击者控制的TLS ClientHello中session_id_len字节作为缓冲区索引而未验证接收数据长度，可能导致远程未认证攻击者发送特制ClientHello与超大会话ID长度读取接收缓冲区之后，导致基于MG_TLS_BUILTIN

CVSS 7.5 · High EPSS 0.61% · P47

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 1

VendorProduct Version RangeStatus
Cesanta Mongoose < 7.22 affected
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I. Basic Information for CVE-2026-11404

Vulnerability Information
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Vulnerability Title
Cesanta Mongoose Out-of-Bounds Read in MG_TLS_BUILTIN ClientHello Session ID Parsing
Source: CVE Program / CVE List V5
Vulnerability Description
Cesanta Mongoose before 7.22 contains an out-of-bounds read in the built-in TLS server function mg_tls_server_recv_hello(), which uses an attacker-controlled session_id_len byte from a TLS ClientHello as a buffer index without validating it against the length of received data. A remote, unauthenticated attacker can send a single crafted ClientHello with an oversized session id length to read past the receive buffer, crashing any HTTPS, MQTTS, or WSS service built on MG_TLS_BUILTIN.
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:H
Source: CVE Program / CVE List V5
Vulnerability Type
跨界内存读
Source: CVE Program / CVE List V5
Vulnerability Title
Cesanta Mongoose 缓冲区错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Cesanta mongoose是爱尔兰Cesanta公司开源的一个嵌入式Web服务器库。 Cesanta Mongoose 7.22之前版本存在缓冲区错误漏洞，该漏洞源于内置TLS服务器函数mg_tls_server_recv_hello()中存在越界读取，该函数使用攻击者控制的TLS ClientHello中session_id_len字节作为缓冲区索引而未验证接收数据长度，可能导致远程未认证攻击者发送特制ClientHello与超大会话ID长度读取接收缓冲区之后，导致基于MG_TLS_BUILTIN
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 0 ~ 7.22 -

II. Public POCs for CVE-2026-11404

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III. Intelligence Information for CVE-2026-11404

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Patches & Fixes for CVE-2026-11404 (1)

Vendor Advisories for CVE-2026-11404 (1)

Vendor Pages for CVE-2026-11404 (1)

IV. Related Vulnerabilities

Same product: Mongoose
Same vendor: Cesanta
Same weakness: CWE-125

V. Comments for CVE-2026-11404

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