CVE-2012-0789 in PHP
Summary
by MITRE
Memory leak in the timezone functionality in PHP before 5.3.9 allows remote attackers to cause a denial of service (memory consumption) by triggering many strtotime function calls, which are not properly handled by the php_date_parse_tzfile cache.
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Analysis
by VulDB Data Team • 12/16/2024
The vulnerability identified as CVE-2012-0789 represents a critical memory leak in PHP's timezone handling functionality that existed in versions prior to 5.3.9. This issue specifically affects the php_date_parse_tzfile cache mechanism which is responsible for parsing and caching timezone information. The flaw occurs when the strtotime function is repeatedly invoked with various timezone specifications, causing the application to accumulate memory without proper cleanup. This vulnerability falls under the CWE-401 category of Improper Release of Memory Before Removing Last Reference, which is a fundamental memory management issue that can lead to resource exhaustion.
The technical implementation of this vulnerability stems from how PHP's date and time functions handle timezone data caching. When the strtotime function processes timezone information, it relies on a cache mechanism to store parsed timezone data for performance optimization. However, the cache implementation did not properly manage memory allocation and deallocation, leading to a gradual accumulation of memory resources that were never released back to the system. Attackers can exploit this by making numerous calls to strtotime with different timezone specifications, each triggering the cache to store additional data without clearing previously stored entries. This behavior creates a memory leak that progressively consumes available system resources.
The operational impact of CVE-2012-0789 is significant as it enables remote attackers to perform denial of service attacks against PHP applications. By continuously triggering strtotime function calls with various timezone parameters, an attacker can cause the target system to consume excessive memory until the application becomes unresponsive or crashes entirely. This vulnerability is particularly dangerous in web applications where user input is processed through strtotime functions, as it can be exploited through simple HTTP requests or API calls. The attack vector is straightforward and requires minimal technical expertise, making it a popular choice for automated denial of service attacks against PHP-based web servers.
Mitigation strategies for this vulnerability require immediate patching of affected PHP installations to versions 5.3.9 or later where the memory leak has been resolved. System administrators should also implement rate limiting mechanisms to prevent excessive calls to date parsing functions and consider monitoring memory usage patterns to detect potential exploitation attempts. Additionally, applications should sanitize and validate timezone inputs to minimize the exposure surface, and implementing proper resource monitoring can help detect when memory consumption reaches abnormal levels. The ATT&CK framework categorizes this as a resource exhaustion technique under the T1499 category of Resource Exhaustion, where attackers leverage application weaknesses to consume system resources and cause service disruption. Organizations should also consider implementing web application firewalls and intrusion detection systems to monitor for patterns indicative of this specific attack vector.