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AIKIDO-2026-593205

openresty is vulnerable to Out-of-bounds Write

Out-of-bounds WriteCVE-2026-55233 Published Aug 12, 2026

75

High Risk

This Affects:

OSopenresty
1.29.2.1 - 1.29.2.4
Fixed in 1.29.2.5
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TL;DR

OpenResty's stream module includes an upstream PROXY protocol v2 patch that builds a binary protocol header before forwarding a connection to an upstream server. When a deployment is configured to emit PROXY protocol v2 to upstreams, the header serialization advances a write pointer through address-family and Type-Length-Value fields without fully validating the remaining space in the preallocated buffer. This lets the routine write past the buffer boundary, which results in a denial of service. The fix adds bounds enforcement so header bytes are only written when sufficient buffer space remains.

Who does this affect?

You are affected if you are running a version in the vulnerable range and your configuration explicitly enables PROXY protocol v2 for upstream connections.

Background info

openresty is vulnerable to Out-of-bounds Write in versions 1.29.2.1 - 1.29.2.4.

How to fix this

Upgrade the openresty/openresty library to the patch version.

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