CVE-2026-103866
Description
A flaw was found in Apache Sling Engine. A remote attacker could perform HTTP request smuggling by sending specially crafted requests containing non-standard percent-encoded characters or invalid character sets. Because the query and form parser continues processing requests despite encountering formatting errors, front-end and back-end systems may interpret request boundaries differently. This desynchronization can allow an attacker to bypass security controls or poison web caches.
Statement
This vulnerability is rated with Low severity because successful HTTP request smuggling requires a specific proxy-to-backend architecture with mismatched request parsing behavior and timing conditions to achieve limited manipulation of adjacent requests. In typical Red Hat deployments, Apache Sling is rarely deployed as a directly exposed public frontend, and exploitation relies on fronting infrastructure forwarding malformed query strings or encoding anomalies rather than rejecting them at the perimeter. Because the underlying flaw does not permit arbitrary code execution, confidential data disclosure, or direct privilege escalation on the host system, the overall security risk remains low.
Mitigation
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
Understanding the Weakness (CWE)
Integrity,Non-Repudiation,Access Control
Technical Impact: Unexpected State; Hide Activities; Bypass Protection Mechanism
An attacker could create HTTP messages to exploit a number of weaknesses including 1) the message can trick the web server to associate a URL with another URL's webpage and caching the contents of the webpage (web cache poisoning attack), 2) the message can be structured to bypass the firewall protection mechanisms and gain unauthorized access to a web application, and 3) the message can invoke a script or a page that returns client credentials (similar to a Cross Site Scripting attack).
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