Intel

AIKIDO-2026-269507

event-listener is vulnerable to Race Condition

Race Condition Pre-CVE
Found by Aikido Intel before public disclosure or CVE publication.
Published Aug 3, 2026

40

Medium Risk

This Affects:

RUSTevent-listener
5.1.0 - 5.4.1
Fixed in 5.4.2
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TL;DR

Affected versions of event-listener unconditionally implement Send and Sync for StackSlot<'_, T>, the stack-allocated listener type created by the listener! macro. That lets a !Send tag set via Event::with_tag be moved to another thread and accessed through StackSlot::wait, causing a data race in safe Rust. The fix adds a T: Send bound on the Send/Sync implementations for StackSlot.

Who does this affect?

You are affected if you are using a version that falls within the vulnerable range and create an Event with Event::with_tag using a !Send tag type, then move a listener!-created StackSlot across threads.

Background info

event-listener is vulnerable to Race Condition in versions 5.1.0 - 5.4.1.

How to fix this

Upgrade the event-listener library to the patch version.

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