CVE-2026-73253: critical vulnerability in cesanta mongoose
Mongoose: TLS Hostname Verification Bypass via Overly Permissive Wildcard Matching
Published
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28Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 9.1epss 0.3%
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.
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
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%