What is CVE-2021-28099?

CVE-2021-28099 is a medium-severity security vulnerability in com.netflix.hollow:hollow (maven), affecting versions <= 6.1.0. No fixed version is listed yet.

How severe is CVE-2021-28099?

CVE-2021-28099 has a CVSS score of 4.4 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.

Which versions of com.netflix.hollow:hollow are affected by CVE-2021-28099?

com.netflix.hollow:hollow (maven) versions <= 6.1.0 is affected.

Is there a fix for CVE-2021-28099?

No fixed version is listed for CVE-2021-28099 yet. Monitor the advisory for updates and apply mitigations in the interim.

Is CVE-2021-28099 exploitable, and should I be worried?

Whether CVE-2021-28099 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk.

What actually determines whether CVE-2021-28099 is exploitable, and how bad it is?

Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.

CVE-2021-28099 in com.netflix.hollow:hollow

Q: How severe is CVE-2021-28099?

CVE-2021-28099 has a CVSS score of 4.4 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.

Q: Which versions of com.netflix.hollow:hollow are affected by CVE-2021-28099?

com.netflix.hollow:hollow (maven) versions <= 6.1.0 is affected.

Q: Is there a fix for CVE-2021-28099?

No fixed version is listed for CVE-2021-28099 yet. Monitor the advisory for updates and apply mitigations in the interim.

Q: Is CVE-2021-28099 exploitable, and should I be worried?

Whether CVE-2021-28099 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk.

Q: What actually determines whether CVE-2021-28099 is exploitable, and how bad it is?

Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.

Summary

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.

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.

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.

CVE-2021-28099 has a CVSS score of 4.4 (Medium). The vector is requires local access, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. No fixed version is listed yet, so configuration controls and monitoring matter more in the interim.

Affected versions

com.netflix.hollow:hollow (<= 6.1.0)

Security releases

Not available

Kodem intelligence

Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.

Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.

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Remediation advice

No fixed version is listed for CVE-2021-28099 yet.

Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.

Frequently Asked Questions

What is CVE-2021-28099? CVE-2021-28099 is a medium-severity security vulnerability in com.netflix.hollow:hollow (maven), affecting versions <= 6.1.0. No fixed version is listed yet.
How severe is CVE-2021-28099? CVE-2021-28099 has a CVSS score of 4.4 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
Which versions of com.netflix.hollow:hollow are affected by CVE-2021-28099? com.netflix.hollow:hollow (maven) versions <= 6.1.0 is affected.
Is there a fix for CVE-2021-28099? No fixed version is listed for CVE-2021-28099 yet. Monitor the advisory for updates and apply mitigations in the interim.
Is CVE-2021-28099 exploitable, and should I be worried? Whether CVE-2021-28099 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
What actually determines whether CVE-2021-28099 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.