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CVE-2026-73253— Mongoose: TLS Hostname Verification Bypass via Overly Permissive Wildcard Matching

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.

Mongoose 是一个嵌入式 Web 服务器和网络库。在 7.22 版本之前，具有父域名通配符证书的中间人攻击者可以利用内置 TLS 栈伪装成更深层的子域，从而欺骗客户端。src/tls_builtin.c 中的 mg_tls_verify_cert_san() 和 mg_tls_verify_cert_cn() 函数调用了 mg_match()，而 mg_match() 中的通配符匹配规则可以跨越 DNS 标签边界，因此像 *.example.com 这样的模式可以匹配 foo.bar.example.com。

CVSS 9.1 · Critical EPSS 0.21% · P12

Possible ATT&CK Techniques 1 AI

T1557 · Adversary-in-the-Middle

Affected Version Matrix 1

VendorProduct Version RangeStatus
cesanta mongoose < 7.22 affected
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I. Basic Information for CVE-2026-73253

Vulnerability Information
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Vulnerability Title
Mongoose: TLS Hostname Verification Bypass via Overly Permissive Wildcard Matching
Source: CVE Program / CVE List V5
Vulnerability Description
Mongoose is an embedded web server and network library. Prior to version 7.22, an on-path network attacker with a wildcard certificate for a parent domain can impersonate deeper subdomains to a client using the built-in TLS stack. The mg_tls_verify_cert_san() and mg_tls_verify_cert_cn() functions in src/tls_builtin.c call mg_match(), whose wildcard can cross DNS label boundaries, so a pattern such as *.example.com can match foo.bar.example.com. The resulting hostname verification bypass permits interception and modification of TLS traffic. This issue is fixed in version 7.22.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
证书验证不恰当
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
cesanta mongoose < 7.22 -

II. Public POCs for CVE-2026-73253

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III. Intelligence Information for CVE-2026-73253

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Patches & Fixes for CVE-2026-73253 (1)

Vendor Advisories for CVE-2026-73253 (1)

Vendor Pages for CVE-2026-73253 (1)

Same Patch Batch · cesanta · 2026-08-20 · 8 CVEs total

CVE-2026-73251 9.3 CRITICAL Mongoose Built-in TLS: CA-bundle certificate chain accepted without any signature verifica
CVE-2026-73257 9.1 CRITICAL Mongoose: Content-Length + Transfer-Encoding coexistence enables request smuggling
CVE-2026-73256 9.1 CRITICAL Mongoose: HTTP/1.0 detection off-by-one enables request smuggling via chunked TE
CVE-2026-73258 6.5 MEDIUM Mongoose: Multipart boundary/header scan logic error in mg_http_next_multipart
CVE-2026-73255 6.5 MEDIUM Mongoose: Path traversal in SSI #include directives enables arbitrary file read
CVE-2026-73254 5.4 MEDIUM Mongoose: Stored XSS via unescaped filenames in directory listing
CVE-2026-73259 5.4 MEDIUM Mongoose: Reflected XSS via decoded URI in directory listing render

IV. Related Vulnerabilities

Same product: mongoose
Same vendor: cesanta
Same weakness: CWE-295

V. Comments for CVE-2026-73253

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