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.

References

• https://nvd.nist.gov/vuln/detail/CVE-2021-28099
• Netflix/hollow#502
• https://github.com/Netflix/security-bulletins/blob/master/advisories/nflx-2021-001.md
• GHSA-j83w-7qr9-wv86