Rust advisories / conquer-once
Vulnerability HighRUSTSEC-2020-0101 · conquer-once
RUSTSEC-2020-0101: conquer-once's OnceCell lacks Send bound for its Sync trait.
Short answerA security vulnerability in the conquer-once crate: conquer-once's OnceCell lacks Send bound for its Sync trait.. High severity (CVSS 7.8). Fixed in 0.3.2: update to a fixed version.
| Crate | conquer-once |
|---|---|
| Type | Vulnerability (memory-corruption, thread-safety) |
| Affected versions | Before 0.3.2. |
| Fixed in | 0.3.2 |
| Severity | High, CVSS 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H |
| Published | 2020-12-22 |
| Last changed | 2023-11-08 |
| Also known as | CVE-2020-36208, GHSA-3jc5-5hc5-33gj |
What to do
- See which version you have:
cargo tree -i conquer-once(it also shows which of your dependencies pulls it in). - Update within your version requirement:
cargo update -p conquer-once. If the fix is a newer major or minor than your requirement allows, raise it in Cargo.toml (for exampleconquer-once = "0.3.2") or update the dependency that pulls it in. - Check again with
cargo audit, or paste your Cargo.lock into our Cargo.toml checker.
Details from the advisory
Affected versions of conquer-once implements Sync for its OnceCell type without restricting it to Sendable types.
This allows non-Send but Sync types such as MutexGuard to be sent across threads leading to undefined behavior and memory corruption in concurrent programs.
The issue was fixed by adding a Send constraint to OnceCell.
References
- Package: crates.io/crates/conquer-once
- Advisory: rustsec.org/advisories/RUSTSEC-2020-0101.html
- Report: github.com/oliver-giersch/conquer-once/issues/3
From the RustSec Advisory Database (CC0-1.0) via the OSV export, downloaded Oct 24, 2026. Severity score computed from the published CVSS vector.
Up next
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