AIKIDO-2026-955118
cesanta.mongoose is vulnerable to HTTP Request Smuggling
91
Critical Risk
This Affects:
cesanta.mongooseTL;DR
The built-in HTTP parser accepts requests that carry both Content-Length and Transfer-Encoding headers, which the HTTP specification says must be treated as an error. Mongoose honors the chunked encoding while a fronting proxy may use Content-Length, producing different request boundaries. An untrusted client can exploit this desync to smuggle a request that the proxy attributes to another connection. The fix rejects requests presenting both headers.
Who does this affect?
You are affected if you are using a version that falls within the vulnerable range and you run the built-in HTTP server behind a reverse proxy that can interpret request boundaries differently.
Background info
cesanta.mongoose is vulnerable to HTTP Request Smuggling in versions 7.2.0 - 7.21.0.
How to fix this
Upgrade the cesanta.mongoose library to the patch version.
Links
GitHub Release
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SOC 2Compliant
ISO 27001Compliant