CVE-2018-1323 in Tomcat JK ISAPI Connector
Summary
by MITRE
The IIS/ISAPI specific code in the Apache Tomcat JK ISAPI Connector 1.2.0 to 1.2.42 that normalised the requested path before matching it to the URI-worker map did not handle some edge cases correctly. If only a sub-set of the URLs supported by Tomcat were exposed via IIS, then it was possible for a specially constructed request to expose application functionality through the reverse proxy that was not intended for clients accessing Tomcat via the reverse proxy.
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Analysis
by VulDB Data Team • 02/21/2023
The vulnerability identified as CVE-2018-1323 resides within the Apache Tomcat JK ISAPI Connector version 1.2.0 through 1.2.42, specifically affecting environments where IIS serves as a reverse proxy for Tomcat applications. This flaw manifests in the path normalization process that occurs within the ISAPI-specific code module, which is responsible for translating requests from IIS to the backend Tomcat server. The issue stems from inadequate handling of edge cases during path normalization, creating a potential bypass mechanism that allows attackers to access restricted application functionality through the reverse proxy configuration.
The technical flaw exploits a path normalization routine that fails to properly account for certain edge cases when processing requested paths before matching them against the URI-worker mapping configuration. This normalization process, which should standardize paths to ensure consistent routing, contains logic gaps that permit malformed or specially crafted requests to bypass intended access controls. When only a subset of Tomcat's URLs are exposed through IIS, the vulnerability becomes particularly dangerous as it enables attackers to construct requests that map to unintended worker configurations, effectively granting access to application resources that should remain protected behind the reverse proxy.
The operational impact of this vulnerability is significant for organizations relying on IIS as a reverse proxy for Tomcat applications, as it creates an unauthorized access vector that could potentially expose sensitive application functionality. Attackers could leverage this weakness to access application components, servlets, or resources that were not meant to be publicly accessible through the reverse proxy configuration. The vulnerability essentially undermines the security boundary established by the reverse proxy setup, allowing lateral movement within the application architecture and potentially leading to data exposure or further exploitation of underlying application vulnerabilities.
Security mitigations for CVE-2018-1323 primarily involve upgrading to Apache Tomcat JK ISAPI Connector version 1.2.43 or later, which contains the necessary fixes for the path normalization edge cases. Organizations should also implement additional defensive measures including strict URI-worker mapping configurations, regular security assessments of reverse proxy setups, and monitoring for anomalous request patterns that might indicate exploitation attempts. The vulnerability aligns with CWE-20, "Improper Input Validation," and represents a path traversal or access control bypass scenario that could be categorized under ATT&CK technique T1071.004 for application layer protocol manipulation, potentially enabling further attack progression through compromised application access.