CVE-2026-73251: critical vulnerability in cesanta mongoose
Mongoose Built-in TLS: CA-bundle certificate chain accepted without any signature verification
Published
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28Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 9.3epss 0.2%
Mongoose is an embedded web server and network library. Prior to 7.23, a network attacker can impersonate a TLS server to a Mongoose client configured with a multi-certificate CA bundle. In src/tls_builtin.c, the mg_tls_init() function stores the bundle in tls->ca_bundle_der while tls->ca_der.len remains zero, and mg_tls_recv_cert() uses tls_bundle_find() to accept a Common Name match without calling mg_tls_verify_cert_signature(). A forged self-signed certificate can therefore satisfy hostname and CertificateVerify checks and enable interception, credential disclosure, traffic modification, and malicious responses. This issue is fixed in version 7.23.
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
Affected products
cesanta · mongooseRelated CVEs — cesanta mongoose
In the same product, most dangerous first.
CVE-2026-73257CRITICALMongoose: Content-Length + Transfer-Encoding coexistence enables request smugglingEPSS 0.7%CVE-2026-73255MEDIUMMongoose: Path traversal in SSI #include directives enables arbitrary file readEPSS 0.7%CVE-2026-73258MEDIUMMongoose: Multipart boundary/header scan logic error in mg_http_next_multipartEPSS 0.5%CVE-2026-73256CRITICALMongoose: HTTP/1.0 detection off-by-one enables request smuggling via chunked TEEPSS 0.4%CVE-2026-73261HIGHMongoose: handle_opt() missing opts[1] > len check — 1-byte OOB read corrupts TCP MSS, silences mg_send() per connectionEPSS 0.4%CVE-2026-73259MEDIUMMongoose: Reflected XSS via decoded URI in directory listing renderEPSS 0.4%