What is CVE-2021-45709?

CVE-2021-45709 is a critical-severity vulnerability in Crypto2 Project, classified under Improper Restriction of Operations within the Bounds of a Memory Buffer. CVSS score: 9.8/10. Published 2021-12-27.

How severe is CVE-2021-45709?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Buffer overflow in Crypto2 Project

CVE-2021-45709

An issue was discovered in the crypto2 crate through 2021-10-08 for Rust. During Chacha20 encryption and decryption, an unaligned read of a u32 may occur.

Vulnerability class: Buffer Overflow

Published 2021-12-27 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.008 (53.5th percentile), scored 2026-10-06.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 53rd percentile — 53.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.008 · newest: 0.008 · change: 0.000

Affected products

Crypto2 Project

Weakness classification (CWE)

CWE-119 — Improper Restriction of Operations within the Bounds of a Memory Buffer

References

rustsec.org/advisories/RUSTSEC-2021-0121.html (Third Party Advisory)
raw.githubusercontent.com/rustsec/advisory-db/main/crates/crypto2/RUSTSEC-2021-… (Third Party Advisory)

Frequently asked questions

What is CVE-2021-45709?: CVE-2021-45709 is a critical-severity vulnerability in Crypto2 Project, classified under Improper Restriction of Operations within the Bounds of a Memory Buffer. CVSS score: 9.8/10. Published 2021-12-27.
How severe is CVE-2021-45709?: Critical severity. CVSS v3 base score is 9.8 out of 10.