CVE-2012-5580 in libproxy
Summary
by MITRE
Format string vulnerability in the print_proxies function in bin/proxy.c in libproxy 0.3.1 might allow context-dependent attackers to cause a denial of service (crash) and possibly execute arbitrary code via format string specifiers in a proxy name, as demonstrated using the http_proxy environment variable or a PAC file.
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Analysis
by VulDB Data Team • 04/03/2022
The CVE-2012-5580 vulnerability represents a critical format string flaw within the libproxy library version 0.3.1, specifically within the print_proxies function located in bin/proxy.c. This vulnerability arises from improper handling of user-supplied input when processing proxy configuration data, creating a dangerous condition where attacker-controlled format specifiers can be interpreted by the application's printf-family functions. The flaw exists in the context of proxy name processing, making it particularly dangerous as it can be exploited through common proxy configuration mechanisms such as the http_proxy environment variable or proxy autoconfiguration files. The vulnerability demonstrates the classic characteristics of format string vulnerabilities where untrusted input is directly passed to formatting functions without proper sanitization or validation.
The technical exploitation of this vulnerability occurs when the libproxy library processes proxy names containing format specifiers such as %s, %d, or other printf-style directives. When these malicious format specifiers are encountered in proxy names, the print_proxies function fails to properly sanitize the input before passing it to printf or similar functions. This allows attackers to manipulate the stack contents and potentially execute arbitrary code with the privileges of the process running the libproxy library. The vulnerability is context-dependent because it requires the application to be using libproxy for proxy configuration and to be processing user-controlled proxy names through the vulnerable function path. The impact extends beyond simple denial of service to include potential code execution, making it a serious security concern for any system that relies on libproxy for network proxy management.
The operational impact of CVE-2012-5580 is significant across multiple system components and attack vectors. Systems using libproxy for proxy configuration are vulnerable when processing proxy names from environment variables, PAC files, or other configuration sources that might contain attacker-controlled data. This vulnerability affects web browsers, network applications, and system utilities that depend on libproxy for proxy resolution. The exploitability is enhanced by the fact that many applications automatically read the http_proxy environment variable, making it trivial for attackers to trigger the vulnerability without requiring direct user interaction. Additionally, the vulnerability can be leveraged in conjunction with other attack vectors, potentially allowing for privilege escalation or information disclosure. The vulnerability's presence in a widely-used library means that numerous applications across different platforms and operating systems could be affected, amplifying the potential impact.
Mitigation strategies for CVE-2012-5580 should focus on both immediate remediation and long-term architectural improvements. The primary recommendation is to upgrade to a patched version of libproxy, as the vulnerability was addressed in subsequent releases through proper input validation and sanitization of proxy names. Organizations should implement strict input validation for any proxy configuration data, ensuring that format specifiers are properly escaped or removed before processing. The use of secure coding practices, including the adoption of functions like snprintf instead of sprintf, can prevent similar vulnerabilities from occurring in the future. Network administrators should also consider implementing monitoring for unusual proxy configuration patterns and establish secure proxy configuration management policies. From a defensive perspective, the vulnerability aligns with CWE-134 which specifically addresses format string vulnerabilities, and the exploitation techniques follow patterns associated with attack tactics in the MITRE ATT&CK framework related to privilege escalation and code execution through library vulnerabilities. Organizations should also consider implementing application whitelisting and runtime protection mechanisms to detect and prevent exploitation attempts.