CVE-2026-94243 in Sling
Summary
by MITRE • 09/23/2026
A vulnerability in Apache Sling Security Bundle: the ReferrerFilter accepts weaker-than-orgin evidence.
This issue affects Apache Sling Security Bundle: before 1.3.2.
Users are recommended to upgrade to version 1.3.2, which fixes the issue.
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Analysis
by VulDB Data Team • 09/23/2026
The vulnerability identified in the Apache Sling Security Bundle prior to version 1.3.2 centers on a flawed implementation of cross-origin request validation within the ReferrerFilter component. This filter is designed to protect web applications by verifying that incoming requests originate from trusted sources, thereby mitigating risks associated with Cross-Site Request Forgery and unauthorized data access. The core technical flaw lies in the logic used to validate the Referer header against a whitelist of allowed origins. Specifically, the implementation accepts evidence derived solely from the Referrer or Host headers as sufficient proof of origin, rather than strictly requiring a match between the request's Origin header and an explicitly defined trusted domain list. This weaker-than-origin validation allows attackers to bypass security controls by manipulating HTTP headers in ways that satisfy the filter’s permissive checks while effectively spoofing the true source of the request.
From a technical perspective, this misconfiguration creates a significant gap in the application's defense-in-depth strategy. By relying on less reliable indicators such as the Referrer header, which can be easily omitted or altered by client-side scripts and certain network intermediaries, the system fails to enforce strict origin isolation. In modern web security standards, the Origin header is considered the authoritative source for determining where a request originated during cross-origin requests, particularly in contexts involving AJAX calls or form submissions initiated from external domains. The failure to strictly validate against this standard allows malicious actors to craft crafted HTTP requests that appear legitimate to the Sling Security Bundle but are actually directed at sensitive administrative interfaces or internal APIs without proper authorization context.
The operational impact of this vulnerability is substantial, particularly for deployments using Apache Sling as a content management system or backend service. An attacker exploiting this flaw could perform unauthorized actions on behalf of authenticated users, such as modifying site configurations, uploading malicious assets, or accessing restricted content. This directly compromises the integrity and confidentiality of the hosted application data. Furthermore, because the vulnerability affects versions prior to 1.3.2, any system running these older builds remains exposed to potential exploitation until a patch is applied. The ease with which this header-based validation can be bypassed means that automated scanning tools or manual penetration testers could quickly identify and exploit this weakness in unpatched environments.
To mitigate this risk, organizations must upgrade the Apache Sling Security Bundle to version 1.3.2 or later, where the ReferrerFilter logic has been corrected to enforce stricter origin validation protocols aligned with current web security best practices. In addition to upgrading, administrators should review their configuration files to ensure that allowed origins are explicitly defined and that no legacy configurations rely on weaker header checks. It is also advisable to implement additional layers of defense such as Content Security Policy headers and strict SameSite cookie attributes to further reduce the attack surface. Regularly monitoring for new security advisories related to Apache Sling components will help maintain a robust security posture against evolving web-based threats.
This vulnerability aligns with CWE-346, which describes an Origin Validation Error where a system fails to properly validate the origin of a request before performing sensitive operations. It also relates to ATT&CK technique T1078, Valid Accounts, as exploitation often involves leveraging valid session tokens or credentials in conjunction with forged requests to gain unauthorized access. By addressing this flaw through timely updates and configuration hardening, security teams can effectively neutralize the threat posed by header manipulation attacks targeting Apache Sling deployments.