AIKIDO-2026-194036
cesanta.mongoose is vulnerable to Out-of-bounds Read
75
High Risk
This Affects:
cesanta.mongooseTL;DR
The built-in TLS server reads the session id length byte from a ClientHello and uses it as a buffer index without checking it against the amount of received data. A single crafted ClientHello with an oversized session id length drives an out-of-bounds read past the receive buffer. This can crash any HTTPS, MQTTS, or WSS service using the built-in TLS backend, and is reachable before authentication. The fix validates the session id length before use.
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) to terminate TLS.
Background info
cesanta.mongoose is vulnerable to Out-of-bounds Read in versions 7.13 - 7.21.
How to fix this
Upgrade the cesanta.mongoose library to the patch version.
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