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CVE-2021-27378

28
FAUCET Score

CVE-2021-27378 is a critical vulnerability in the rand_core Rust crate, affecting versions prior to 0.6.2. It stems from improper buffer-length checks in the read_u32_into and read_u64_into functions, potentially leading to random number generators being seeded with insufficient data. With a CVSS score of 9.8 (CRITICAL), this vulnerability is remotely exploitable with low attack complexity, allowing for complete compromise of confidentiality, integrity, and availability. There is currently no evidence of active exploitation, publicly available exploit code, or significant community discussion surrounding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
>= 0.6.0, < 0.6.2CPE matchmatch criteria
cpe:2.3:a:rand_core_project:rand_core:*:*:*:*:*:rust:*:*

CVSS Data

CVSS version used by this source: 3.1

9.8CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
1.23%
Probability of exploitation in next 30 days
EPSS Percentile
65.7%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0123 is in the 52nd percentile among its peer group of 36,897 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (7)

microsoftpatch availablevia msrc
Product: azl3 librsvg2 2.50.3-4 on Azure Linux 3.0Fixed in: 2.58.1-1
microsoftpatch availablevia msrc
Product: 19743-17084Fixed in: 2.58.1-1
microsoftpatch availablevia msrc
Product: 18817-17084Fixed in: 2.58.1-1
microsoftpatch availablevia msrc
Product: Azure Linux 3.0 ARMFixed in: 2.58.1-1
microsoftpatch availablevia msrc
Product: azl3 librsvg2 2.58.1-1 on Azure Linux 3.0Fixed in: 2.58.1-1
microsoftpatch availablevia msrc
Product: Azure Linux 3.0 x64Fixed in: 2.58.1-1
rustpatch availablevia ghsa
Product: rand_coreFixed in: 0.6.2

Vendor Advisories (3)

microsoft2024-Jun/CVE-2021-27378

CVE-2021-27378

Jun 11, 2024
rustGHSA-w7j2-35mf-95p7critical

Incorrect check on buffer length in rand_core

Aug 25, 2021
microsoft2021-Feb/CVE-2021-27378Critical

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.

Feb 9, 2021

References

rustsec.org / advisories/RUSTSEC-2021-0023.html
Third Party Advisory