CVE-2017-5659 in Traffic Server
Summary
by MITRE
Apache Traffic Server before 6.2.1 generates a coredump when there is a mismatch between content length and chunked encoding.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 11/29/2022
Apache Traffic Server version 6.2.1 and earlier contains a critical vulnerability that manifests when processing HTTP requests with inconsistent content length and chunked encoding parameters. This vulnerability stems from the server's improper handling of malformed HTTP transfer encoding, specifically when the Content-Length header value does not align with the actual chunked data being transmitted. The flaw represents a classic buffer over-read condition that occurs during the parsing and validation of HTTP request headers, creating an opportunity for denial of service attacks that can crash the server process and generate coredump files.
The technical implementation of this vulnerability involves the server's HTTP parser encountering a scenario where chunked encoding is specified in the Transfer-Encoding header while a Content-Length header is also present. When these two conflicting parameters are processed together, the parser fails to properly validate the consistency between the declared content length and the actual chunked data stream. This mismatch causes the server to allocate memory buffers based on the Content-Length value, but then attempt to read or process data according to the chunked encoding rules, resulting in memory access violations that trigger process termination and core dump generation.
From an operational impact perspective, this vulnerability presents a significant risk to web infrastructure services that rely on Apache Traffic Server for content delivery and proxy operations. The denial of service condition can be easily exploited by sending a crafted HTTP request containing conflicting content length and chunked encoding headers, causing the server to crash and become unavailable to legitimate users. This vulnerability directly maps to CWE-129 and CWE-131 within the Common Weakness Enumeration framework, specifically addressing issues related to insufficient boundary checking and improper handling of buffer sizes. The attack surface is particularly concerning for high-traffic web applications where a single malicious request could disrupt service availability for extended periods.
The exploitation of CVE-2017-5659 aligns with several techniques documented in the MITRE ATT&CK framework under the T1499 category for network denial of service attacks. Attackers can leverage this vulnerability to perform sustained service disruption attacks against web servers, potentially leading to business impact and revenue loss. The vulnerability's impact extends beyond simple service interruption as the coredump generation creates additional system overhead and can be used for further analysis by attackers to understand the server configuration. Organizations should implement immediate mitigations including upgrading to Apache Traffic Server 6.2.1 or later, implementing request filtering rules to detect and block malformed HTTP requests, and establishing monitoring systems to detect unusual coredump generation patterns that may indicate exploitation attempts. Additionally, network-level controls such as web application firewalls and intrusion detection systems can be configured to identify and block requests containing conflicting content length and chunked encoding headers, providing defense-in-depth protection against this specific vulnerability.