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RUSTSEC-2026-0221: event-listener allows !Send tags to cross thread boundaries via StackSlot #4762

Description

@github-actions

event-listener allows !Send tags to cross thread boundaries via StackSlot

Details
Status unsound
Package event-listener
Version 5.4.1
URL smol-rs/event-listener#163
Date 2026-07-13

Affected versions of event-listener unconditionally implement Send and
Sync for StackSlot<'_, T>, the stack-allocated listener type created
by the listener! macro.

This allows a !Send tag type set via Event::with_tag to be moved to
another thread and accessed via StackSlot::wait, causing a data race in safe
code.

See advisory page for additional details.

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