CVE-2021-28099: Hollow Insecure Temporary File Vulnerability

MODERATE
Advisory Identifier: GHSA-9295-mhf3-v33m
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CVSS 4.4
CWE-377
Published
Advisory Summary

CVE-2021-28099 is a MODERATE (CVSS 4.4) insecure temporary file vulnerability (CWE-377: Insecure Temporary File) affecting Hollow libraries in the Maven ecosystem. The issue involves insecure temporary file in netflix oss hollow. Remediation is available in the latest vendor maintenance releases.

CVE-2021-28099 at a Glance

CVE Identifier CVE-2021-28099
GHSA Identifier GHSA-9295-mhf3-v33m
Severity MODERATE
CVSS v3.1 Base Score 4.4
CWE Classification CWE-377: Insecure Temporary File
Affected Product Hollow
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 4.4

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N).

Attack Vector Local (AV:L)
Attack Complexity Low (AC:L)
Privileges Required Low (PR:L)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality Low (C:L)
Integrity Low (I:L)
Availability None (A:N)

How to Fix CVE-2021-28099

To remediate this vulnerability, upgrade all affected Hollow dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

com.netflix.hollow:hollow fixed: Latest secure release 
<dependency>
    <groupId>com.netflix.hollow</groupId>
    <artifactId>hollow</artifactId>
    <version>Latest secure release</version>
</dependency>
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

mvn dependency:tree -Dincludes=com.netflix.hollow

How to Check if You Are Affected

To determine whether your Java application is affected by CVE-2021-28099, inspect your build dependencies using the Maven Dependency Plugin:

mvn dependency:tree -Dincludes=com.netflix.hollow

Analyze the terminal output to locate any version of Hollow in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than the patched release), your application is affected.

Note: The mvn dependency:tree -Dincludes=com.netflix.hollow command inspects the resolved dependency graph declared in your project's POM files; it does not perform automated security scanning or inspect runtime dynamic classpaths. Always verify runtime container classpaths and shaded JARs.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-377: Insecure Temporary File, where creating and using insecure temporary files can leave application and system data vulnerable to attack. In Hollow, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

> 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.

CVE-2021-28099 Affected Hollow Versions

1 component(s)
Product / Package Ecosystem Affected Versions Fixed Version
com.netflix.hollow:hollow
maven/com.netflix.hollow/hollow
Maven
≤ 6.1.0

References

GitHub Advisory / Wiki ADVISORY
https://github.com/JLLeitschuh/security-research/security/advisories/GHSA-j83w-7qr9-wv86
NVD — CVE-2021-28099 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-28099
Hollow Source Repository REPOSITORY
https://github.com/Netflix/hollow/issues/502
GitHub Advisory / Wiki ADVISORY
https://github.com/Netflix/security-bulletins/blob/master/advisories/nflx-2021-001.md

Frequently Asked Questions

What is CVE-2021-28099?
CVE-2021-28099 is a security vulnerability in Hollow involving Insecure temporary file in Netflix OSS Hollow under CWE-377: Insecure Temporary File.
Which Hollow versions are affected?
Affected versions include releases prior to current release patches across affected packages: com.netflix.hollow:hollow.
What version fixes CVE-2021-28099?
Upgrading to current release patches (or the latest patched release for your respective branch) resolves the vulnerability.
Is hollow affected?
Yes, com.netflix.hollow:hollow is affected in releases prior to Latest secure release. Upgrade your dependency to Latest secure release or later.
What is the CVSS score of CVE-2021-28099?
CVE-2021-28099 has a CVSS v3.1 base score of 4.4 (MODERATE) with vector string CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N.
What CWE is associated with CVE-2021-28099?
CVE-2021-28099 is classified under CWE-377: Insecure Temporary File (Creating and using insecure temporary files can leave application and system data vulnerable to attack.).
How can I check Maven dependencies for CVE-2021-28099?
Run the dependency tree command: 'mvn dependency:tree -Dincludes=com.netflix.hollow'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-9295-mhf3-v33m",
  "modified" : "2023-08-08T19:54:40Z",
  "published" : "2021-03-29T18:25:26Z",
  "aliases" : [ "CVE-2021-28099" ],
  "summary" : "Insecure temporary file in Netflix OSS Hollow",
  "details" : "> ID: NFLX-2021-001\n> Title: Local information disclosure in Hollow\n> Release Date: 2021-03-23\n> Credit: Security Researcher @JLLeitschuh\n\n# Overview\n\nSecurity 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.\n\n# Impact\n\nAn 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.\n\n# Description\n\nSince 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.\n\n# Workarounds and Fixes\n\nAvoid running Hollow in configurations that share a filesystem with less-trusted processes. May be fixed in a future release.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "com.netflix.hollow:hollow"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "last_affected" : "6.1.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/JLLeitschuh/security-research/security/advisories/GHSA-j83w-7qr9-wv86"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-28099"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/Netflix/hollow/issues/502"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/Netflix/security-bulletins/blob/master/advisories/nflx-2021-001.md"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-377" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-03-24T23:39:18Z",
    "nvd_published_at" : "2021-03-23T21:15:00Z"
  }
}