CVE-2015-5740 in Google
Summary
by MITRE
The net/http library in net/http/transfer.go in Go before 1.4.3 does not properly parse HTTP headers, which allows remote attackers to conduct HTTP request smuggling attacks via a request with two Content-length headers.
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Analysis
by VulDB Data Team • 01/04/2023
The vulnerability identified as CVE-2015-5740 resides within the net/http library of the Go programming language, specifically in the transfer.go file. This flaw represents a critical security issue that affects Go versions prior to 1.4.3, where the HTTP header parsing mechanism fails to properly handle duplicate Content-Length headers. The vulnerability stems from the library's inability to correctly process HTTP requests containing multiple Content-Length header fields, creating a potential avenue for malicious actors to exploit HTTP request smuggling techniques. This weakness directly impacts the integrity of HTTP communication and can be leveraged to manipulate how HTTP requests are processed by servers.
The technical flaw manifests when an HTTP request contains two Content-Length headers with different values, a scenario that violates HTTP protocol specifications but is not properly handled by the vulnerable Go library. When the net/http library processes such requests, it fails to properly validate or normalize these duplicate headers, allowing attackers to craft malicious requests that can confuse HTTP proxies and intermediaries. The library's inadequate header parsing logic means that it may use the first or second Content-Length value inconsistently, creating opportunities for request smuggling where an attacker can inject additional requests or manipulate the request processing flow. This behavior aligns with CWE-129 and CWE-444, which address improper input validation and HTTP protocol violations respectively.
The operational impact of this vulnerability extends beyond simple protocol violations, as it enables sophisticated attack vectors that can compromise web applications and reverse proxy configurations. Attackers can exploit this weakness to bypass security controls, perform unauthorized operations, or manipulate data flow within HTTP communication channels. The vulnerability is particularly dangerous in environments where Go applications serve as intermediaries or where HTTP request smuggling could be used to access restricted resources or perform unauthorized actions. Network security systems that rely on proper HTTP header validation may be deceived by the malformed requests, potentially leading to unauthorized access or data leakage. This vulnerability directly maps to techniques described in the ATT&CK framework under HTTP protocol manipulation and request smuggling tactics.
Mitigation strategies for CVE-2015-5740 primarily focus on upgrading affected Go installations to version 1.4.3 or later, where the HTTP header parsing has been corrected to properly handle duplicate Content-Length headers. Organizations should also implement additional network-level protections such as web application firewalls that can detect and block malformed HTTP requests, and deploy robust HTTP header validation at proxy and load balancer levels. Security teams should conduct thorough vulnerability assessments of all Go applications in their environment, particularly those handling external HTTP traffic, and ensure that proper input sanitization is implemented at multiple layers of the application stack. The fix implemented in Go 1.4.3 demonstrates proper handling of HTTP header normalization, ensuring that duplicate Content-Length headers are either rejected or properly merged according to HTTP specifications.