CVE-2026-8646 in WebSphere Application Server
Summary
by MITRE • 06/22/2026
IBM WebSphere Application Server 9.0 and 8.5 and IBM WebSphere Application Server - Liberty 17.0.0.3 through 26.0.0.6 are vulnerable to HTTP request smuggling. A remote attacker could smuggle a specially crafted request to the application server thereby allowing the attacker to bypass security controls, spoof identity, escalate privilege, and expose sensitive information.
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Analysis
by VulDB Data Team • 06/22/2026
IBM WebSphere Application Server versions 9.0 and 8.5 along with IBM WebSphere Application Server Liberty versions 17.0.0.3 through 26.0.0.6 contain a critical HTTP request smuggling vulnerability that enables remote attackers to manipulate how requests are processed across the application server. This vulnerability stems from improper handling of HTTP message boundaries and transfer encoding mechanisms, allowing malicious actors to craft requests that appear legitimate to the front-end proxy while being interpreted differently by the backend application server. The flaw exists in the HTTP request parsing logic where the server fails to properly validate or normalize incoming HTTP headers, particularly those related to content length, transfer encoding, and chunked encoding parameters.
The technical implementation of this vulnerability allows attackers to exploit inconsistencies between how different components within the WebSphere ecosystem process HTTP requests. When a maliciously crafted request is sent through the vulnerable server, it can cause the application server to interpret multiple requests as a single request or split a single request into multiple interpretations. This behavior creates opportunities for bypassing authentication mechanisms, as the server may process one part of the request for authentication while another part executes with elevated privileges. The vulnerability specifically relates to CWE-444 HTTP Request Smuggling, which is classified under the OWASP Top Ten 2017 as a critical security weakness.
The operational impact of this vulnerability extends beyond simple information disclosure, creating pathways for privilege escalation and identity spoofing attacks within enterprise environments. Attackers can leverage this weakness to bypass security controls that rely on proper HTTP request handling, potentially gaining access to restricted resources or executing unauthorized operations within the application server environment. The attack surface is particularly concerning in multi-tiered applications where WebSphere serves as an intermediary between external clients and internal backend services. This vulnerability enables attackers to perform actions such as accessing administrative interfaces, reading sensitive data from other users' sessions, or manipulating application state through carefully crafted request smuggling techniques.
Organizations should implement immediate mitigations including enabling strict HTTP header validation on all incoming requests, configuring proper proxy settings with explicit content length handling, and deploying web application firewalls that can detect and block suspicious HTTP request patterns. The ATT&CK framework categorizes this vulnerability under T1566 Initial Access - Phishing, as attackers often use crafted HTTP requests to establish footholds within networks. Security teams should also consider implementing network segmentation to limit the impact of potential exploitation and deploy monitoring solutions specifically designed to detect HTTP smuggling attempts. Regular updates to IBM WebSphere Application Server versions are critical, with patches addressing the underlying HTTP parsing inconsistencies and improved validation mechanisms for handling transfer encoding headers. The vulnerability demonstrates how fundamental protocol handling flaws can create cascading security issues throughout enterprise infrastructure, emphasizing the importance of proper input validation at all layers of application communication.