CVE-2015-3185 in Xcode
Summary
by MITRE
The ap_some_auth_required function in server/request.c in the Apache HTTP Server 2.4.x before 2.4.14 does not consider that a Require directive may be associated with an authorization setting rather than an authentication setting, which allows remote attackers to bypass intended access restrictions in opportunistic circumstances by leveraging the presence of a module that relies on the 2.2 API behavior.
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Analysis
by VulDB Data Team • 06/16/2022
The vulnerability described in CVE-2015-3185 affects the Apache HTTP Server version 2.4.x before 2.4.14 and stems from a flaw in the ap_some_auth_required function located in server/request.c. This issue represents a critical authorization bypass vulnerability that exploits a behavioral inconsistency between Apache 2.2 and 2.4 API implementations. The core problem manifests when the server processes Require directives within configuration contexts where authorization settings are mixed with authentication settings, creating opportunities for attackers to circumvent access controls that were intended to be enforced.
The technical flaw lies in how Apache 2.4 handles the interpretation of Require directives during request processing. Specifically, the ap_some_auth_required function fails to properly distinguish between authorization and authentication requirements when processing configuration directives. This function is designed to determine whether authentication is required for a particular request, but it incorrectly treats authorization settings as if they were authentication requirements. When a module operates under the 2.2 API behavior pattern, it may inadvertently rely on the older interpretation where authorization and authentication contexts were not clearly separated, creating a mismatch in the 2.4 implementation that attackers can exploit.
The operational impact of this vulnerability extends beyond simple access control bypasses and represents a significant threat to server security integrity. Attackers can leverage this flaw to gain unauthorized access to protected resources by crafting requests that take advantage of the inconsistent handling of Require directives. The vulnerability is particularly dangerous because it operates opportunistically, meaning it may not be consistently exploitable but can be triggered under specific conditions where certain modules are present and active. This characteristic makes the vulnerability particularly challenging to detect and remediate, as it may not manifest in all deployment scenarios.
The security implications align with CWE-284, which addresses improper access control vulnerabilities, and relates to the ATT&CK technique T1078.101 for Valid Accounts - Default Accounts. This vulnerability essentially allows unauthorized access through improper handling of authentication and authorization contexts, potentially enabling attackers to escalate privileges or access sensitive resources that should be restricted. The flaw demonstrates a breakdown in the principle of least privilege and could enable attackers to bypass security controls that are fundamental to protecting server resources and data confidentiality.
Mitigation strategies for CVE-2015-3185 require immediate patching of affected Apache HTTP Server installations to version 2.4.14 or later, where the issue has been resolved through proper handling of Require directive contexts. Organizations should also conduct thorough configuration reviews to identify and correct any instances where authentication and authorization settings might be improperly mixed in their Apache configurations. Security teams should implement monitoring for unusual access patterns that might indicate exploitation attempts and consider implementing additional access control layers beyond the basic Apache configuration to provide defense-in-depth. The fix addresses the root cause by ensuring that the ap_some_auth_required function properly differentiates between authentication and authorization requirements, thereby preventing the exploitation path that allows bypass of intended access restrictions.