CVE-2019-16276 in Google
Summary
by MITRE
Go before 1.12.10 and 1.13.x before 1.13.1 allow HTTP Request Smuggling.
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Analysis
by VulDB Data Team • 05/09/2025
The vulnerability identified as CVE-2019-16276 represents a critical HTTP Request Smuggling issue affecting Go programming language versions prior to 1.12.10 and 1.13.1. This flaw resides in the HTTP request parsing and handling mechanisms within the Go standard library, specifically impacting how the runtime processes HTTP headers and request boundaries. The vulnerability enables attackers to manipulate HTTP requests in ways that can bypass security controls and potentially access restricted resources. The issue stems from improper handling of HTTP header parsing, particularly when dealing with malformed or specially crafted header values that can cause the HTTP parser to misinterpret request boundaries and content length specifications.
The technical implementation of this vulnerability exploits weaknesses in Go's HTTP request processing logic where the parser fails to properly validate or normalize HTTP headers before processing. Attackers can craft malicious HTTP requests containing carefully constructed header values that cause the server to interpret the same request as multiple distinct requests or to process requests with incorrect boundaries. This occurs particularly when the application uses the standard library's http.Request parsing functionality without additional validation layers. The vulnerability can be leveraged through various attack vectors including proxy servers, load balancers, and web applications that rely on Go's built-in HTTP handling capabilities. According to CWE classification, this maps to CWE-444, which describes improper handling of HTTP requests, and aligns with ATT&CK technique T1190 for Proxy Execution through HTTP smuggling attacks.
The operational impact of CVE-2019-16276 extends beyond simple request manipulation to potentially enable more sophisticated attacks including cache poisoning, session hijacking, and bypassing authentication mechanisms. When exploited, this vulnerability allows attackers to inject malicious content or commands into HTTP responses that should be isolated from each other, creating opportunities for cross-site scripting, data leakage, and unauthorized access to protected resources. The vulnerability is particularly dangerous in environments where Go applications serve as reverse proxies or act as intermediaries between clients and backend services, as it can enable attackers to manipulate traffic flows and access internal systems that should remain isolated. Organizations running vulnerable Go applications face significant risk of data breaches and service disruption, especially in cloud environments where HTTP traffic is frequently routed through multiple proxy layers.
Mitigation strategies for CVE-2019-16276 require immediate patching of affected Go versions to 1.12.10 or 1.13.1, which contain the necessary fixes to properly handle HTTP header parsing and boundary detection. Additionally, organizations should implement additional defensive measures including HTTP header validation, request normalization, and monitoring for suspicious HTTP patterns that might indicate exploitation attempts. Network security controls such as web application firewalls should be configured to detect and block malformed HTTP requests that exhibit characteristics associated with HTTP smuggling attacks. The implementation of proper input validation and sanitization at all layers of the application stack becomes crucial, particularly for applications that process HTTP traffic directly. Organizations should also consider implementing strict HTTP header policies and regularly audit their Go applications for proper HTTP request handling to prevent similar vulnerabilities from emerging in future code implementations.