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Fencer Vulns
critical 9.8

CVE-2021-27378 json

Incorrect check on buffer length in rand_core

published 2021-02-12 5 y ago modified 2026-06-17 4 mo ago also GHSA-w7j2-35mf-95p7 , RUSTSEC-2021-0023 , EUVD-2021-1910

cvss
9.8
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
1.2%
EPSS 1.2% chance of exploitation in 30 days, percentile 69%
public exploits
0
none known

Summary

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.

Patch / fix

  • crates.io rand_core 0.6.2
  • rand_core_project rand_core 0.6.2
  • librsvg2 Azure Linux 3.0 2.58.1-1

azure linux advisories AZL-41851

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

Exploit prediction

1.24% chance of exploitation in the next 30 days, higher than 69% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 7.5 AV:N/AC:L/Au:N/C:P/I:P/A:P
OSV 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
GitHub 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected packages

ecosystem package affected fixed in
crates.io rand_core
>=0.6.0, <0.6.2
0.6.2

Classification

Weakness
  • CWE-131 Incorrect Calculation of Buffer Size
  • CWE-330 Use of Insufficiently Random Values

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.