Vulnerability CriticalRUSTSEC-2021-0023 · rand_core
RUSTSEC-2021-0023: Incorrect check on buffer length when seeding RNGs
Short answerA security vulnerability in the rand_core crate: Incorrect check on buffer length when seeding RNGs. Critical severity (CVSS 9.8). Fixed in 0.6.2: update to a fixed version.
| Crate | rand_core |
|---|---|
| Type | Vulnerability (crypto-failure) |
| Affected versions | From 0.6.0 before 0.6.2. |
| Fixed in | 0.6.2 |
| Severity | Critical, CVSS 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
| Published | 2021-02-12 |
| Last changed | 2023-11-08 |
| Also known as | CVE-2021-27378, GHSA-w7j2-35mf-95p7 |
| Affected functions | rand_core::le::read_u32_into, rand_core::le::read_u64_into |
What to do
- See which version you have:
cargo tree -i rand_core(it also shows which of your dependencies pulls it in). - Update within your version requirement:
cargo update -p rand_core. If the fix is a newer major or minor than your requirement allows, raise it in Cargo.toml (for examplerand_core = "0.6.2") 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
Summary: rand_core::le::read_u32_into and read_u64_into have incorrect checks on the source buffer length, allowing the destination buffer to be under-filled.
Implications: some downstream RNGs, including Hc128Rng (but not the more widely used ChaCha*Rng), allow seeding using the SeedableRng::from_seed trait-function with too short keys.
References
- Package: crates.io/crates/rand_core
- Advisory: rustsec.org/advisories/RUSTSEC-2021-0023.html
- Web: github.com/rust-random/rand/pull/1096
From the RustSec Advisory Database (CC0-1.0) via the OSV export, downloaded Oct 24, 2026. Severity score computed from the published CVSS vector.
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