RUSTSEC-2026-0138: Unsound access to padding bytes while serializing date/time values using the Mysql backend

What to do

1. See which version you have: cargo tree -i diesel-async (it also shows which of your dependencies pulls it in).
2. Update within your version requirement: cargo update -p diesel-async. If the fix is a newer major or minor than your requirement allows, raise it in Cargo.toml (for example diesel-async = "0.9.0") 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

Diesel-async uses the mysql-async crate for interacting with Mysql compatible databases. This library already provides access to deserialized data for date/time releated types. Diesel-async then translated these deserialized data back to their serialized binary representation to hook into diesels desearialization framework.

While serializing these data/time values again Diesel-async relied on a cast between the MysqlTime #[repr(C)] struct (defined by Diesel) and a byte array. As this cast exposes padding bytes contained in this struct, this is undefined behaviour.

This vulnerability affects any user deserializing date/time values using the Mysql backend and diesel-async.

This affects any usage of the following functions with a AsyncMysqlConnection provided by diesel-async:

• diesel::serialize::FromSql<Timestamp, Mysql>
• diesel::serialize::FromSql<Time, Mysql>
• diesel::serialize::FromSql<Date, Mysql>
• diesel::serialize::FromSql<DateTime, Mysql>

Mitigation

The preferred mitigation to the outlined problem is to update to Diesel-async version 0.9.0 or newer, which includes fixes for the problem.

Resolution

Diesel-async now just calls a safe serialization method provided by Diesel 2.3.9 and newer

References

• Package: crates.io/crates/diesel-async
• Advisory: rustsec.org/advisories/RUSTSEC-2026-0138.html
• Advisory: github.com/diesel-rs/diesel_async/security/advisories/GHSA-ff9q-rm55-q7qr

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 diesel-async

• VulnerabilityGHSA-ff9q-rm55-q7qr · 2026-05-07diesel-async may expose uninitialized padding bytes for MySQL temporal columns

Full security history of diesel-async