Intel

AIKIDO-2026-268979

reactor-core is vulnerable to Denial of Service (DoS)

Denial of Service (DoS)CVE-2026-47857 Published Aug 21, 2026

59

Medium Risk

This Affects:

JAVAreactor-core
0.0.1 - 3.8.6
Fixed in 3.8.7
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TL;DR

reactor-core Flux.windowTimeout with fair backpressure can hang after a 20-bit index wrap on a long-lived stream. A client that keeps the stream open and manipulates read speed can stop element processing without an error. Held subscriptions then exhaust resources. The patch prevents the wrap-around from permanently stalling the operator.

Who does this affect?

You are affected if you are using a version that falls within the vulnerable range and you use Flux.windowTimeout with fair backpressure enabled.

Background info

reactor-core is vulnerable to Denial of Service (DoS) in versions 0.0.1 - 3.8.6.

How to fix this

Upgrade the io.projectreactor:reactor-core library to the patch version.

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