CVE-2011-3267 in PHP
Summary
by MITRE
PHP before 5.3.7 does not properly implement the error_log function, which allows context-dependent attackers to cause a denial of service (application crash) via unspecified vectors.
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Analysis
by VulDB Data Team • 11/18/2021
The vulnerability identified as CVE-2011-3267 represents a critical flaw in PHP's error_log function implementation that existed prior to version 5.3.7. This issue stems from improper handling of the error_log function parameters, creating a scenario where malicious input can trigger application instability. The vulnerability operates within the broader context of PHP's logging mechanisms and demonstrates how seemingly benign error handling functions can become attack vectors when not properly secured. The flaw specifically affects PHP versions earlier than 5.3.7, making it a significant concern for systems running outdated PHP implementations.
The technical implementation flaw occurs when the error_log function processes its parameters without adequate validation or sanitization of input data. This improper parameter handling creates conditions where specially crafted input can cause the PHP application to crash or become unresponsive. The vulnerability is context-dependent, meaning its exploitation requires specific conditions or inputs that trigger the problematic code path within the error_log function. Attackers can leverage this weakness to craft malicious requests that, when processed by vulnerable PHP applications, result in application termination or system instability.
From an operational impact perspective, this vulnerability enables attackers to perform denial of service attacks against PHP-based web applications without requiring elevated privileges or complex exploitation techniques. The attack surface is broad as any application using PHP and the error_log function is potentially vulnerable. When exploited, the vulnerability can cause complete application downtime, rendering web services unavailable to legitimate users. The impact extends beyond simple service disruption as application crashes can also lead to data loss, increased system load from repeated failures, and potential cascading effects on dependent systems. Organizations running vulnerable PHP applications face significant risk of service interruption and potential reputational damage.
Mitigation strategies for CVE-2011-3267 primarily focus on immediate PHP version upgrades to 5.3.7 or later, which contain the necessary patches addressing the error_log implementation flaw. System administrators should conduct comprehensive vulnerability assessments to identify all PHP installations running vulnerable versions and prioritize their upgrade schedules. Additionally, implementing proper input validation and sanitization practices for error_log function calls can provide temporary protection while upgrades are being implemented. Organizations should also consider deploying web application firewalls and intrusion detection systems to monitor for exploitation attempts. The vulnerability aligns with CWE-20, which addresses improper input validation, and can be mapped to ATT&CK technique T1499.004, which covers network disruption through application or service interruption. Regular security patch management processes should be implemented to prevent similar vulnerabilities from arising in the future, emphasizing the importance of keeping PHP installations up to date with the latest security releases.