CVE-2018-20073 in Chrome
Summary
by MITRE
Use of extended attributes in downloads in Google Chrome prior to 72.0.3626.81 allowed a local attacker to read download URLs via the filesystem.
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Analysis
by VulDB Data Team • 06/28/2020
This vulnerability in Google Chrome prior to version 72.0.3626.81 represents a significant security flaw related to how the browser handles extended attributes in downloaded files. The issue stems from insufficient validation of file system metadata during download operations, creating an avenue for local attackers to potentially access sensitive information. Extended attributes in Unix-like file systems provide additional metadata storage beyond standard file permissions and ownership, and the vulnerability exploited improper handling of these attributes when processing downloaded content.
The technical flaw manifests when Chrome processes downloaded files that contain extended attributes, particularly those related to download URLs or metadata. Attackers could manipulate these extended attributes to inject or store information that would otherwise be restricted. This weakness allows a local attacker to read download URLs from the filesystem through the extended attribute mechanism, effectively bypassing normal access controls that should prevent such information disclosure. The vulnerability specifically impacts the browser's file system interaction layer where it stores and retrieves metadata associated with downloaded content.
The operational impact of this vulnerability extends beyond simple information disclosure, as download URLs often contain sensitive routing information, authentication tokens, or other data that could be leveraged for further attacks. A local attacker with read access to the file system could extract these URLs and potentially use them for phishing attacks, credential harvesting, or as part of a broader exploitation chain. This type of vulnerability particularly affects environments where Chrome is used in multi-user scenarios or where file system access is not strictly controlled. The risk is elevated in enterprise environments where download management and security policies are critical components of overall security posture.
The vulnerability aligns with CWE-200, which addresses improper exposure of sensitive information, and relates to broader categories of file system security issues in web browsers. From an ATT&CK framework perspective, this maps to techniques involving privilege escalation and information gathering through local system access. The flaw demonstrates how seemingly minor implementation details in file system handling can create substantial security risks. Organizations should implement immediate mitigations including updating to Chrome version 72.0.3626.81 or later, conducting thorough security assessments of download handling processes, and monitoring for unauthorized file system modifications. Additionally, system administrators should review and tighten file system access controls, particularly for directories where browser downloads are stored, to limit potential exploitation vectors.