CVE-2002-0842 in Application Server
Summary
by MITRE
Format string vulnerability in certain third party modifications to mod_dav for logging bad gateway messages (e.g. Oracle9i Application Server 9.0.2) allows remote attackers to execute arbitrary code via a destination URI that forces a "502 Bad Gateway" response, which causes the format string specifiers to be returned from dav_lookup_uri() in mod_dav.c, which is then used in a call to ap_log_rerror().
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Analysis
by VulDB Data Team • 09/13/2025
This vulnerability resides within the Apache module mod_dav and specifically affects third-party modifications such as those found in Oracle9i Application Server 9.0.2. The issue stems from improper handling of format string arguments during error logging operations, creating a critical security flaw that can be exploited remotely. The vulnerability manifests when a malicious client sends a specially crafted destination URI that triggers a "502 Bad Gateway" HTTP response code, which then causes the vulnerable code path to process user-supplied input as a format string specifier.
The technical flaw occurs in the dav_lookup_uri() function within mod_dav.c, where user-controlled data from the destination URI is directly incorporated into the logging mechanism without proper sanitization or validation. When this function processes a malformed URI that results in a 502 error response, the format string specifiers contained within the user input are subsequently passed to ap_log_rerror(), which interprets these specifiers as format directives rather than literal text. This fundamental failure in input validation creates a classic format string vulnerability that allows attackers to manipulate memory contents and execute arbitrary code on the affected server.
The operational impact of this vulnerability is severe as it provides remote attackers with complete system compromise capabilities. An attacker can leverage this flaw to execute arbitrary code with the privileges of the web server process, potentially leading to full system control, data exfiltration, or further network penetration. The vulnerability is particularly dangerous because it requires minimal user interaction to trigger and can be exploited through standard HTTP requests. This type of vulnerability falls under CWE-134, which specifically addresses format string vulnerabilities where format specifiers are derived from external input sources.
The attack vector involves sending a maliciously crafted HTTP request with a destination URI that causes the server to generate a 502 Bad Gateway error response, thereby triggering the vulnerable code path. According to ATT&CK framework, this represents a privilege escalation technique through application layer exploitation. The vulnerability demonstrates poor input validation practices and improper error handling in web server components, making it an attractive target for automated exploitation tools. Organizations using affected versions of Oracle9i Application Server or other third-party modifications to mod_dav should immediately implement mitigations including patching the affected software components and implementing proper input validation measures to prevent user-supplied data from being processed as format string arguments.
Mitigation strategies should focus on updating to patched versions of the affected software components, implementing strict input validation for URI parameters, and configuring web server logging to prevent format string exploitation. Security administrators should also consider implementing network-level protections such as intrusion detection systems and web application firewalls to detect and block malicious requests targeting this vulnerability. The fix typically involves ensuring that user-supplied input is properly escaped or sanitized before being passed to logging functions, preventing the accidental interpretation of format specifiers. This vulnerability underscores the critical importance of proper input validation and secure coding practices in server-side applications, particularly in components that handle external user input and generate error messages.