What is CVE-2021-28099?

CVE-2021-28099 is a medium-severity vulnerability in Netflix Hollow, classified under Use of Insufficiently Random Values. CVSS score: 4.4/10. Published 2021-03-23.

How severe is CVE-2021-28099?

Medium severity. CVSS v3 base score is 4.4 out of 10.

Vulnerability in Netflix Hollow

CVE-2021-28099

In Netflix OSS Hollow, since the Files.exists(parent) is run before creating the directories, an attacker can pre-create these directories with wide permissions. Additionally, since an insecure source of randomness is used, the file names to be created can be deterministically calculated.

Published 2021-03-23 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 4.4 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N.

EPSS exploit prediction

EPSS: 0.002 (13.9th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 14th percentile — 13.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: 0.000

Affected products

Netflix Hollow
Netflix Oss Hollow — versions All versions

Weakness classification (CWE)

CWE-330 — Use of Insufficiently Random Values

References

github.com/Netflix/security-bulletins/blob/master/advisories/nflx-2021-001.md (Third Party Advisory)

Frequently asked questions

What is CVE-2021-28099?: CVE-2021-28099 is a medium-severity vulnerability in Netflix Hollow, classified under Use of Insufficiently Random Values. CVSS score: 4.4/10. Published 2021-03-23.
How severe is CVE-2021-28099?: Medium severity. CVSS v3 base score is 4.4 out of 10.