CVE-2021-28099

Local file disclosure and modification via predictable directories

Published Mar 23, 2021 · Updated Aug 3, 2024

Information disclosure in Netflix Hollow allows local users to read or modify temporary files through pre-created directories. Temporary-file creation calls Files.exists(parent) before directory creation and uses predictable names, accepting attacker-set permissions. A local user who shares the filesystem and can create directories and set permissions can inspect or alter data written by the Hollow process.

CVSS severity4.4
Medium
EPSS probability0.24%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Information disclosure in Netflix Hollow allows local users to read or modify temporary files through pre-created directories. Temporary-file creation calls Files.exists(parent) before directory creation and uses predictable names, accepting attacker-set permissions. A local user who shares the filesystem and can create directories and set permissions can inspect or alter data written by the Hollow process.

The record

CVE
CVE-2021-28099
Published
Mar 23, 2021
Updated
Aug 3, 2024
Vendor
Netflix
Product
Hollow
Classifications
CWE-330, T1005, T1565.001
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 23, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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  1. Affected versionversion=All versions

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Netflix · Hollowversion=All versions

Published CVSS scores

3.6NIST National Vulnerability DatabaseAV:L/AC:L/Au:N/C:P/I:P/A:N
4.4NIST National Vulnerability DatabaseCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-330Use of Insufficiently Random Values
T1005Data from Local System
T1565.001Stored Data Manipulation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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