CVE-2005-4852 in eZ publish
Summary
by MITRE
The siteaccess URIMatching implementation in eZ publish 3.5 through 3.8 before 20050812 converts all non-alphanumeric characters in a URI to _ (underscore), which allows remote attackers to bypass access restrictions by inserting certain characters in a URI, as demonstrated by a request for /admin:de, which matches a rule allowing only /admin_de to access /admin.
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Analysis
by VulDB Data Team • 08/04/2017
The vulnerability described in CVE-2005-4852 represents a critical access control flaw within the eZ publish content management system version 3.5 through 3.8. This issue stems from the siteaccess URIMatching implementation which processes URIs through a normalization mechanism that indiscriminately converts all non-alphanumeric characters to underscores. The flaw exists in the core authentication and authorization framework that governs how users access different sections of the web application based on their permissions and the defined access rules. This normalization process creates a predictable pattern where certain URI sequences can be manipulated to bypass intended access restrictions, fundamentally undermining the security controls designed to protect administrative sections of the application.
The technical exploitation of this vulnerability occurs through URI manipulation techniques that take advantage of the character conversion process. When a URI containing special characters such as colons is processed by the system, the non-alphanumeric characters are automatically converted to underscores, transforming the original request path into an alternative form that matches existing access rules. In the specific example provided, a request for /admin:de gets converted to /admin_de, which then matches an access rule that permits access to the /admin section, thereby allowing unauthorized users to bypass the intended restrictions. This behavior demonstrates a classic input sanitization weakness where the system's attempt to normalize input inadvertently creates security loopholes rather than addressing them.
The operational impact of this vulnerability extends beyond simple unauthorized access, as it can enable attackers to escalate privileges and gain access to sensitive administrative functions within the eZ publish platform. Security researchers have identified this as a weakness in the application's authorization model, where the URI parsing and matching logic fails to properly validate or restrict the characters that can be used in access control paths. This flaw can be particularly dangerous in environments where administrative access is restricted to specific user roles, as it allows attackers to potentially bypass these controls entirely by crafting malicious URI requests. The vulnerability essentially creates a backdoor mechanism that can be exploited to access protected sections of the application regardless of the intended access controls.
This vulnerability aligns with CWE-20, which describes improper input validation, and represents a specific case of how character encoding and normalization can create security weaknesses in access control systems. The flaw also corresponds to ATT&CK technique T1078 which covers valid accounts and legitimate credentials, as attackers can exploit this weakness to gain access to administrative functions that should be restricted. Organizations using eZ publish versions 3.5 through 3.8 should immediately implement patches or workarounds that address the URI normalization logic to prevent attackers from manipulating access control rules through character substitution. The recommended mitigation involves either disabling the automatic character conversion in the URIMatching implementation or implementing more robust validation mechanisms that prevent unauthorized URI sequences from matching legitimate access rules. Additionally, administrators should review and tighten access control policies to ensure that even if such attacks were to succeed, the damage would be limited by proper privilege management and monitoring.