RUSTSEC-2024-0019: Tokens for named pipes may be delivered after deregistration

What to do

1. See which version you have: cargo tree -i mio (it also shows which of your dependencies pulls it in).
2. Update within your version requirement: cargo update -p mio. If the fix is a newer major or minor than your requirement allows, raise it in Cargo.toml (for example mio = "0.8.11") or update the dependency that pulls it in.
3. Check again with cargo audit, or paste your Cargo.lock into our Cargo.toml checker.

Details from the advisory

Impact

When using named pipes on Windows, mio will under some circumstances return invalid tokens that correspond to named pipes that have already been deregistered from the mio registry. The impact of this vulnerability depends on how mio is used. For some applications, invalid tokens may be ignored or cause a warning or a crash. On the other hand, for applications that store pointers in the tokens, this vulnerability may result in a use-after-free.

For users of Tokio, this vulnerability is serious and can result in a use-after-free in Tokio.

The vulnerability is Windows-specific, and can only happen if you are using named pipes. Other IO resources are not affected.

Affected versions

This vulnerability has been fixed in mio v0.8.11.

All versions of mio between v0.7.2 and v0.8.10 are vulnerable.

Tokio is vulnerable when you are using a vulnerable version of mio AND you are using at least Tokio v1.30.0. Versions of Tokio prior to v1.30.0 will ignore invalid tokens, so they are not vulnerable.

Workarounds

Vulnerable libraries that use mio can work around this issue by detecting and ignoring invalid tokens.

Technical details

When an IO resource registered with mio has a readiness event, mio delivers that readiness event to the user using a user-specified token. Mio guarantees that when an IO resource is deregistered, then it will never return the token for that IO resource again. However, for named pipes on windows, mio may sometimes deliver the token for a named pipe even though the named pipe has been previously deregistered.

This vulnerability was originally reported in the Tokio issue tracker: tokio-rs/tokio#6369 This vulnerability was fixed in: tokio-rs/mio#1760

Thank you to @rofoun and @radekvit for discovering and reporting this issue.

References

• Package: crates.io/crates/mio
• Advisory: rustsec.org/advisories/RUSTSEC-2024-0019.html
• Web: github.com/tokio-rs/mio/pull/1760

From the RustSec Advisory Database (CC0-1.0) via the OSV export, downloaded Oct 24, 2026. Severity score computed from the published CVSS vector.

Other advisories for mio

• Unsound MediumRUSTSEC-2020-0081 · 2020-11-02`mio` invalidly assumes the memory layout of std::net::SocketAddr

Full security history of mio