CVE-2017-7658 in REST Data Services
Summary
by MITRE
In Eclipse Jetty Server, versions 9.2.x and older, 9.3.x (all non HTTP/1.x configurations), and 9.4.x (all HTTP/1.x configurations), when presented with two content-lengths headers, Jetty ignored the second. When presented with a content-length and a chunked encoding header, the content-length was ignored (as per RFC 2616). If an intermediary decided on the shorter length, but still passed on the longer body, then body content could be interpreted by Jetty as a pipelined request. If the intermediary was imposing authorization, the fake pipelined request would bypass that authorization.
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Analysis
by VulDB Data Team • 08/23/2024
The vulnerability identified as CVE-2017-7658 affects Eclipse Jetty Server implementations across multiple version branches including 9.2.x and older, 9.3.x (excluding HTTP/1.x configurations), and 9.4.x (specifically HTTP/1.x configurations). This security flaw stems from the server's improper handling of HTTP content-length headers and chunked encoding mechanisms, creating a potential authorization bypass scenario that could be exploited by malicious actors. The vulnerability resides in the HTTP request parsing logic where Jetty's behavior deviates from established RFC standards, specifically RFC 2616 which governs HTTP/1.1 implementations. The core issue manifests when multiple content-length headers are present in a request, or when both content-length and chunked encoding headers are simultaneously included, leading to inconsistent processing of request bodies.
The technical flaw operates through a specific parsing anomaly within Jetty's HTTP message handling architecture. When two content-length headers are encountered, the server ignores the second header value while processing the request, which creates a discrepancy between the expected and actual body length. Similarly, when both content-length and chunked encoding headers are present, Jetty's implementation fails to properly prioritize the chunked encoding directive as mandated by RFC 2616. This inconsistency allows an attacker to craft requests where an intermediary proxy might enforce a shorter content-length limit while still transmitting the full body content. The server's subsequent interpretation of the excess body content as a pipelined request creates a fundamental security vulnerability that can be leveraged for unauthorized access.
The operational impact of this vulnerability extends beyond simple request parsing errors and represents a serious authorization bypass threat within web application security frameworks. When intermediaries such as load balancers, reverse proxies, or security appliances enforce content-length restrictions, the vulnerability allows attackers to craft malicious requests that appear to conform to length limits while actually containing additional content that gets interpreted as separate requests. This behavior creates a potential attack vector where an attacker could inject a second request containing authorization credentials or administrative commands after the initial legitimate request, effectively bypassing the authorization mechanisms that should have protected the first request. The vulnerability specifically affects environments where HTTP/1.x configurations are used, making it particularly relevant for legacy web applications and systems that have not been updated to newer HTTP protocol implementations.
Organizations utilizing affected Jetty versions should implement immediate mitigation strategies to address this vulnerability. The primary recommendation involves upgrading to patched versions of Jetty that properly implement RFC 2616 compliance for content-length and chunked encoding header handling. Security administrators should also consider implementing additional network-level controls such as proxy configuration changes that enforce consistent content-length handling and prevent the passage of content that exceeds declared limits. The vulnerability aligns with CWE-129 and CWE-130 categories related to improper handling of input boundaries and improper handling of HTTP headers, while also mapping to ATT&CK techniques involving protocol manipulation and credential access through request smuggling. Network monitoring should be enhanced to detect anomalous request patterns that might indicate exploitation attempts, particularly focusing on requests with conflicting content-length headers or unusual pipelining behavior. Organizations should also conduct thorough security assessments of their middleware stacks to identify any other potential components that might be vulnerable to similar header parsing inconsistencies.