How severe is CVE-2021-27378?

CVE-2021-27378 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-27378 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (66th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-27378?

CVE-2021-27378 affects Rand Core Project Rand Core. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-27378?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2021-27378 published?

CVE-2021-27378 was published on 2021-02-18 and last updated on 2026-06-17.

CVE-2021-27378

CVE-2021-27378 is a critical-severity vulnerability in Rand Core Project Rand Core with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-131.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 1% (66th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-131
Affected product: Rand Core Project Rand Core
Published: 2021-02-18
Last modified: 2026-06-17

Description

An issue was discovered in the rand_core crate before 0.6.2 for Rust. Because read_u32_into and read_u64_into mishandle certain buffer-length checks, a random number generator may be seeded with too little data.

Frequently asked questions

What is CVE-2021-27378?: An issue was discovered in the rand_core crate before 0.6.2 for Rust. Because read_u32_into and read_u64_into mishandle certain buffer-length checks, a random number generator may be seeded with too little data.
How severe is CVE-2021-27378?: CVE-2021-27378 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-27378 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (66th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-27378?: CVE-2021-27378 affects Rand Core Project Rand Core. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-27378?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2021-27378 published?: CVE-2021-27378 was published on 2021-02-18 and last updated on 2026-06-17.

References

https://rustsec.org/advisories/RUSTSEC-2021-0023.html

Affected products (1)

cpe:2.3:a:rand_core_project:rand_core:*:*:*:*:*:rust:*:*

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