AIKIDO-2026-664083
cesanta.mongoose is vulnerable to Improper Certificate Validation
74
High Risk
This Affects:
cesanta.mongooseTL;DR
The built-in TLS client verifies certificate hostnames with a generic pattern matcher whose wildcard matches across dot separators. A wildcard in a certificate SAN or CN therefore matches subdomains of arbitrary depth, contrary to certificate wildcard rules. A network man-in-the-middle holding a broad wildcard certificate can impersonate hostnames it should not match. The fix restricts wildcard matching to a single DNS label.
Who does this affect?
You are affected if you are using a version that falls within the vulnerable range and you use the built-in TLS backend (MG_TLS_BUILTIN) as a client that validates server certificates.
Background info
cesanta.mongoose is vulnerable to Improper Certificate Validation in versions 7.14 - 7.21.
How to fix this
Upgrade the cesanta.mongoose library to the patch version.
Links
GitHub Release
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