CVE-2026-11710 in WebSphere Application Server
Summary
by MITRE • 09/18/2026
IBM WebSphere Application Server 8.5 is affected by an HTTP request smuggling vulnerability due to improper handling of Content-Length headers.
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Analysis
by VulDB Data Team • 09/18/2026
The IBM WebSphere Application Server version 8.5 contains a critical security flaw classified as an HTTP Request Smuggling vulnerability, specifically stemming from the improper parsing and validation of Content-Length headers within incoming HTTP requests. This type of vulnerability arises when there is a discrepancy in how different network components interpret request boundaries, allowing malicious actors to manipulate the sequence or interpretation of HTTP messages flowing through reverse proxies, load balancers, or firewalls before they reach the application server itself. In this specific instance, the flaw lies in the server's inability to consistently determine where one HTTP request ends and another begins when Content-Length headers are malformed, duplicated, or conflicting with other header fields such as Transfer-Encoding. This ambiguity creates a window of opportunity for attackers to inject their own requests into the stream, effectively bypassing security controls that rely on strict request boundary detection.
From a technical perspective, this vulnerability aligns closely with CWE-436, which denotes Interpretation Conflict, and is often associated with HTTP Request Smuggling techniques documented in industry frameworks like MITRE ATT&CK under tactics involving Initial Access or Defense Evasion. The core mechanism involves an attacker sending a specially crafted request that exploits the difference between how the front-end proxy and the back-end WebSphere Application Server interpret header fields. For example, if a proxy strips certain headers or interprets chunked encoding differently than the backend server, an attacker can hide malicious payloads within what appears to be a legitimate response or inject unauthorized requests into another user's session stream. This misalignment allows the smuggled request to be processed by WebSphere as part of a subsequent valid transaction, leading to potential data leakage, privilege escalation, or complete compromise of the underlying application logic.
The operational impact of this vulnerability is severe and multifaceted. Attackers can exploit HTTP Request Smuggling to perform session hijacking by injecting requests that appear to originate from authenticated users, thereby gaining unauthorized access to sensitive resources without valid credentials. Additionally, it enables cache poisoning attacks where an attacker manipulates the caching layer to serve malicious content or outdated information to other victims, potentially facilitating phishing campaigns or malware distribution. In more advanced scenarios, this flaw can be leveraged for server-side request forgery (SSRF), allowing attackers to probe internal network services that are not directly exposed to the internet but are accessible by the WebSphere Application Server. The ability to smuggle requests also undermines integrity controls and audit logs, as the injected traffic may bypass standard logging mechanisms or appear indistinguishable from legitimate administrative actions, complicating forensic analysis and incident response efforts.
To mitigate this risk, immediate action is required at both the infrastructure and application levels. Organizations should apply the latest security patches provided by IBM for WebSphere Application Server 8.5 to address the header parsing logic flaws. Simultaneously, network-level defenses must be hardened; reverse proxies and load balancers should be configured to strictly enforce consistent HTTP/1.1 or HTTP/2 standards, rejecting any requests with ambiguous or conflicting Content-Length headers before they reach the application server. Implementing strict input validation on all incoming HTTP messages is crucial, ensuring that only well-formed requests are processed. Furthermore, deploying Web Application Firewalls (WAF) with rules specifically tuned to detect request smuggling patterns can provide an additional layer of defense by identifying and blocking anomalous header combinations indicative of exploitation attempts. Regular security audits and penetration testing focused on HTTP protocol compliance will help identify residual misconfigurations that could be exploited despite these mitigations.