CVE-2016-10635 in broccoli-closure
Summary
by MITRE
broccoli-closure is a Closure compiler plugin for Broccoli. broccoli-closure before 1.3.1 downloads binary resources over HTTP, which leaves it vulnerable to MITM attacks. It may be possible to cause remote code execution (RCE) by swapping out the requested binary with an attacker controlled binary if the attacker is on the network or positioned in between the user and the remote server.
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Analysis
by VulDB Data Team • 02/09/2020
The vulnerability identified as CVE-2016-10635 affects broccoli-closure, a popular Closure compiler plugin for the Broccoli build tool used in web development workflows. This plugin serves as an interface between the Broccoli build system and Google's Closure Compiler, enabling developers to optimize their JavaScript code during the build process. The security flaw stems from the plugin's implementation of binary resource downloading mechanisms that utilize unencrypted HTTP protocols instead of secure HTTPS connections. This design choice creates a significant attack surface that exposes users to man-in-the-middle (MITM) vulnerabilities during the automated dependency resolution and binary fetching processes.
The technical flaw manifests in the plugin's failure to implement secure communication channels when downloading binary resources required for the Closure compiler operations. When broccoli-closure attempts to fetch necessary binaries from remote servers, it defaults to using HTTP connections that lack encryption and authentication mechanisms. This vulnerability maps directly to CWE-319, which addresses the exposure of sensitive information through improper use of network protocols, and specifically relates to CWE-200, which covers the exposure of sensitive information to an unauthorized actor. The absence of proper transport layer security allows attackers positioned within the network traffic path to intercept, modify, or replace the downloaded binary files with malicious alternatives without detection.
The operational impact of this vulnerability extends beyond simple data interception, as it potentially enables remote code execution within the build environment. When an attacker successfully substitutes a legitimate binary with a malicious one, they can inject arbitrary code that executes during the build process, potentially compromising the entire development workflow. This scenario represents a critical security risk because build systems often have elevated privileges and access to sensitive development environments. The vulnerability aligns with ATT&CK technique T1059.001, which covers command and script injection, and T1566.001, covering spearphishing via social engineering, as attackers could potentially exploit this weakness through network-based attacks or compromised upstream dependencies. The remote code execution capability makes this vulnerability particularly dangerous in continuous integration environments where automated builds occur frequently and may be triggered by various network-accessible events.
Mitigation strategies for this vulnerability require immediate remediation through upgrading to broccoli-closure version 1.3.1 or later, which implements secure HTTPS connections for binary downloads. Organizations should also consider implementing network-level security controls such as SSL/TLS inspection and monitoring for suspicious network traffic patterns. The fix addresses the core issue by ensuring that all binary resources are downloaded over encrypted channels, preventing attackers from intercepting or modifying the download process. Additionally, developers should implement proper dependency verification mechanisms including checksum validation and digital signatures to provide defense-in-depth against potential supply chain attacks. Security teams should also monitor build systems for unauthorized modifications and implement network segmentation to limit exposure of build environments to untrusted network segments, as this vulnerability could be exploited through various attack vectors including compromised network infrastructure or DNS hijacking scenarios.