# GHSA-ff9q-rm55-q7qr: diesel-async may expose uninitialized padding bytes for MySQL temporal columns > diesel-async leaks uninitialized memory when reading MySQL temporal columns, potentially exposing sensitive data to attackers. - **Severity:** Not scored - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 7 May 2026 ## What is GHSA-ff9q-rm55-q7qr? GHSA-ff9q-rm55-q7qr is a vulnerability in diesel-async, published on 7 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official description ### Summary diesel-async exposes uninitialized stack padding to safe code on every read of a MySQL `DATE`, `TIME`, `DATETIME`, or `TIMESTAMP` column. Reading that buffer is undefined behavior, and the leaked bytes can contain stale heap/stack contents, so this is both a soundness bug and a potential information-disclosure vector. ### Details In `diesel-async/src/mysql/row.rs` (lines 65-103), `MysqlRow::get` builds a `MysqlTime` from the parsed `mysql_async::Value` and then fabricates the byte buffer that downstream `FromSql` impls expect like this: ```rust let date = MysqlTime::new(/* fields from Value::Date / Value::Time */); let buffer = unsafe { let ptr = &date as *const MysqlTime as *const u8; let slice = std::slice::from_raw_parts(ptr, std::mem::size_of::()); slice.to_vec() }; ``` `MysqlTime` is `#[repr(C)]` with 3 bytes of padding after `bool neg` (Linux x86_64, offsets 0x21..0x23). The literal construction leaves that padding uninitialized, and `to_vec()` carries it into a `Vec` that becomes the `MysqlValue`'s backing buffer, reachable from safe code via `MysqlValue::as_bytes() -> &[u8]`. `diesel` itself avoids this by going through `MaybeUninit::::zeroed()` + `ptr::copy_nonoverlapping` (see `diesel/src/mysql/value.rs:43-94`); the same pattern would fix this. Alternatively, write the bytes diesel's `FromSql` reads without round-tripping through a `MysqlTime` value. ### PoC `Cargo.toml`: ```toml [dependencies] diesel = { version = "~2.3.0", default-features = false, features = ["mysql_backend"] } diesel-async = { version = "=0.8.0", features = ["mysql"] } mysql_common = { version = "0.35", default-features = false } ``` `src/main.rs`: ```rust use diesel::row::{Field, Row}; use diesel_async::{AsyncConnectionCore, AsyncMysqlConnection}; use mysql_common::{constants::ColumnType, packets::Column, prelude::FromRow, value::Value}; type MysqlRow = ::Row<'static, 'static>; fn main() { let cols = std::sync::Arc::from([Column::new(ColumnType::MYSQL_TYPE_DATE)]); let raw = mysql_common::row::new_row(vec![Value::Date(2024, 1, 1, 0, 0, 0, 0)], cols); let row: MysqlRow = FromRow::from_row(raw); let field = row.get(0).unwrap(); let bytes = field.value().unwrap().as_bytes(); let _: u64 = bytes.iter().map(|&b| b as u64).sum(); // UB: hits padding } ``` Miri output: ``` error: Undefined Behavior: reading memory at alloc844[0x21..0x22], but memory is uninitialized at [0x21..0x22], and this operation requires initialized memory --> src/main.rs:14:37 | 14 | let _: u64 = bytes.iter().map(|&b| b as u64).sum(); // UB: hits padding | ^ Undefined Behavior occurred here | = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information = note: stack backtrace: 0: main::{closure#0} at src/main.rs:14:37: 14:38 1: std::iter::adapters::map::map_fold::<&u8, u64, u64, {closure@src/main.rs:14:35: 14:39}, {closure@::sum, {closure@src/main.rs:14:35: 14:39}>>::{closure#0}}>::{closure#0} at /home/paolobarbolini/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/iter/adapters/map.rs:88:28: 88:34 2: as std::iter::Iterator>::fold::::sum, {closure@src/main.rs:14:35: 14:39}>>::{closure#0}}>::{closure#0}}> at /home/paolobarbolini/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/slice/iter/macros.rs:279:27: 279:85 3: , {closure@src/main.rs:14:35: 14:39}> as std::iter::Iterator>::fold::::sum, {closure@src/main.rs:14:35: 14:39}>>::{closure#0}}> at /home/paolobarbolini/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/iter/adapters/map.rs:128:9: 128:50 4: ::sum::, {closure@src/main.rs:14:35: 14:39}>> at /home/paolobarbolini/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/iter/traits/accum.rs:52:17: 56:18 5: , {closure@src/main.rs:14:35: 14:39}> as std::iter::Iterator>::sum:: at /home/paolobarbolini/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/iter/traits/iterator.rs:3676:9: 3676:23 6: main at src/main.rs:14:18: 14:55 Uninitialized memory occurred at alloc844[0x21..0x22], in this allocation: alloc844 (Rust heap, size: 48, align: 1) { 0x00 │ e8 07 00 00 01 00 00 00 01 00 00 00 00 00 00 00 │ ................ 0x10 │ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 │ ................ 0x20 │ 00 __ __ __ 01 00 00 00 00 00 00 00 __ __ __ __ │ .░░░........░░░░ } ``` ### Impact Soundness bug in safe API surface of `diesel-async`'s MySQL backend. Affects every user of `AsyncMysqlConnection` whose queries return a temporal column. AI disclosure: this issue was found via Claude Code running Claude Opus 4.7. ## Which versions are affected by GHSA-ff9q-rm55-q7qr? 2 open source packages ship an affected version, including diesel-async. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `diesel-async` | crates.io | From 0.1.0 | 0.9.0 | | `diesel-async` | crates.io | From 0.1.0 | 0.9.0 | ## How do I fix GHSA-ff9q-rm55-q7qr? Upgrade diesel-async to 0.9.0 or later. ## Is GHSA-ff9q-rm55-q7qr being exploited? There is no known exploitation of GHSA-ff9q-rm55-q7qr in the wild and no public exploit code. ## Fix prompt for AI coding agents ```text Check this codebase for GHSA-ff9q-rm55-q7qr and fix it if it is affected. What it is: GHSA-ff9q-rm55-q7qr is a vulnerability in diesel-async, published on 7 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim. Exploitation: There is no known exploitation of GHSA-ff9q-rm55-q7qr in the wild and no public exploit code. Affected packages and fixed versions: - diesel-async (crates.io): affected from 0.1.0; fixed in 0.9.0 - diesel-async (crates.io): affected from 0.1.0; fixed in 0.9.0 Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/GHSA-ff9q-rm55-q7qr/ (Markdown: https://insights.sbomify.com/GHSA-ff9q-rm55-q7qr/index.md) ``` ## Sources - OSV: https://osv.dev/vulnerability/GHSA-ff9q-rm55-q7qr --- From sbomify Insights: https://insights.sbomify.com/GHSA-ff9q-rm55-q7qr/ Summaries are generated and may contain mistakes; the official description above is the record.