CVE-2016-5737 in Puppet Module for Gerrit
Summary
by MITRE
The Gerrit configuration in the Openstack Puppet module for Gerrit (aka puppet-gerrit) improperly marks text/html as a safe mimetype, which might allow remote attackers to conduct cross-site scripting (XSS) attacks via a crafted review.
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Analysis
by VulDB Data Team • 05/13/2026
The vulnerability identified as CVE-2016-5737 resides within the OpenStack Puppet module for Gerrit, specifically concerning the configuration of MIME type handling during web request processing. This issue stems from an insecure default configuration where the system incorrectly categorizes text/html content as a safe mimetype, creating a potential vector for cross-site scripting attacks. The flaw manifests in how the Puppet module manages Gerrit's web interface security settings, particularly in the context of review submission and display mechanisms that process user-provided content through web forms and API endpoints.
The technical implementation of this vulnerability occurs at the web application level where user-generated content containing malicious scripts can be injected into review comments or other editable fields. When the Gerrit system processes these inputs and displays them within the HTML context, the improper MIME type handling allows attackers to bypass security restrictions that would normally prevent execution of malicious JavaScript code. This misconfiguration essentially removes the protective barriers that should prevent user-submitted content from being interpreted as executable code, enabling attackers to craft malicious reviews containing embedded scripts that execute in the context of other users' browsers.
The operational impact of this vulnerability extends beyond simple XSS exploitation as it represents a critical security weakness in OpenStack's infrastructure automation tools. Organizations relying on Puppet-managed Gerrit deployments face significant risks when this module is used in production environments, particularly those handling sensitive code review processes or containing privileged information. The vulnerability affects the integrity of the code review process itself, potentially allowing attackers to steal session cookies, perform unauthorized actions on behalf of legitimate users, or redirect victims to malicious sites while maintaining the appearance of legitimate system interactions.
Mitigation strategies for this vulnerability require immediate attention to the Puppet module configuration files that control Gerrit's security settings. Administrators should update their puppet-gerrit module versions to include proper MIME type handling and ensure that text/html content is not automatically marked as safe for execution. The remediation process involves reviewing and modifying the security configuration parameters within the Puppet manifests, specifically focusing on the content filtering and sanitization rules that govern how user-submitted content is processed and displayed. Additionally, implementing proper input validation and output encoding mechanisms within the Gerrit configuration will help prevent similar issues from occurring in other components of the system.
This vulnerability aligns with CWE-79, which describes cross-site scripting flaws in web applications, and demonstrates how configuration management tools can inadvertently introduce security weaknesses when default settings are not properly secured. The issue also relates to ATT&CK technique T1566, specifically the use of malicious content delivery through web interfaces, as it enables attackers to leverage the web-based review system to deliver malicious payloads. Organizations should consider implementing automated security scanning of their Puppet manifests and configuration files to identify similar misconfigurations that could lead to privilege escalation or data compromise through web-based attack vectors. The remediation process should include comprehensive testing of the fixed configuration to ensure that legitimate functionality remains intact while eliminating the XSS attack surface created by the improper MIME type handling.