CVE-2021-28099
Insecure temporary file in Netflix OSS Hollow
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.
Attack profile
How easy it is to exploit
- Attack vector
- Local
- Complexity
- Low
- Privileges needed
- Low
- User interaction
- None
What an attacker can affect
- Confidentiality
- Low
- Integrity
- Low
- Availability
- None
Exploit likelihood
What each source reports
NVD Score used
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.
- Record
CVE-2021-28099- CVSS 3.1
- 4.4 Medium
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N - CVSS 2.0
- 3.6 Low
AV:L/AC:L/Au:N/C:P/I:P/A:N - Weakness
- CWE-330
- Updated
- 2026-11-02
CVE List No score
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.
- Record
CVE-2021-28099- Updated
- 2026-11-02
EUVDEUVD-2021-0635 No score
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.
- Record
EUVD-2021-0635- Updated
- 2026-11-03
GitHub AdvisoriesGHSA-9295-mhf3-v33m
Insecure temporary file in Netflix OSS Hollow
ID: NFLX-2021-001 Title: Local information disclosure in Hollow Release Date: 2021-03-23 Credit: Security Researcher @JLLeitschuh
Overview
Security researcher @JLLeitschuh reported that Netflix Hollow (a Netflix OSS project available here: https://github.com/Netflix/hollow) writes to a local temporary directory before validating the permissions on it.
Impact
An attacker with the ability to create directories and set permissions on the local filesystem could pre-create this directory and read or modify anything written there by the Hollow process.
Description
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.
Workarounds and Fixes
Avoid running Hollow in configurations that share a filesystem with less-trusted processes. May be fixed in a future release.
- Record
GHSA-9295-mhf3-v33m- CVSS 3.1
- 4.4 Medium
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N - Weakness
- CWE-377
- Updated
- 2026-11-02
OSVGHSA-9295-mhf3-v33m
Insecure temporary file in Netflix OSS Hollow
ID: NFLX-2021-001 Title: Local information disclosure in Hollow Release Date: 2021-03-23 Credit: Security Researcher @JLLeitschuh
Overview
Security researcher @JLLeitschuh reported that Netflix Hollow (a Netflix OSS project available here: https://github.com/Netflix/hollow) writes to a local temporary directory before validating the permissions on it.
Impact
An attacker with the ability to create directories and set permissions on the local filesystem could pre-create this directory and read or modify anything written there by the Hollow process.
Description
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.
Workarounds and Fixes
Avoid running Hollow in configurations that share a filesystem with less-trusted processes. May be fixed in a future release.
- Record
GHSA-9295-mhf3-v33m- CVSS 3.1
- 4.4 Medium
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N - Weakness
- CWE-377
- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
com.netflix.hollow:hollowMaven |
through 6.1.0 | None known |
com.netflix.hollow:hollowMaven |
through 6.1.0, plus listed versions 2.0.02.0.12.0.22.0.32.0.4 Show 45 moreShow less2.0.52.1.02.1.12.10.02.11.02.11.12.12.02.14.02.14.12.15.02.15.12.15.22.16.02.16.12.16.32.16.42.16.52.16.62.16.72.17.12.2.02.2.12.2.22.2.32.2.42.2.52.3.02.3.12.4.02.4.12.4.22.4.32.4.42.5.02.5.12.5.22.5.32.5.42.6.02.6.12.6.102.6.112.6.32.6.42.6.5 |
None known |
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2021-28099 is a medium vulnerability (CVSS 4.4) in Netflix Hollow, published March 23, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.25%, the 16th percentile. No source names a fixed version.
References
Left out here: 103 versions. The JSON record has them.