CVE-2012-0788 in PHP
Summary
by MITRE
The PDORow implementation in PHP before 5.3.9 does not properly interact with the session feature, which allows remote attackers to cause a denial of service (application crash) via a crafted application that uses a PDO driver for a fetch and then calls the session_start function, as demonstrated by a crash of the Apache HTTP Server.
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Analysis
by VulDB Data Team • 12/17/2024
The vulnerability identified as CVE-2012-0788 represents a critical flaw in PHP's PDO (PHP Data Objects) implementation that specifically affects versions prior to 5.3.9. This issue manifests in the improper interaction between PDO row handling and PHP's session management system, creating a condition where malicious applications can trigger application crashes through carefully crafted requests. The vulnerability operates at the intersection of database abstraction layer functionality and session handling mechanisms, making it particularly dangerous in web server environments where both features are commonly utilized.
The technical root cause of this vulnerability lies in how PHP's PDORow class manages memory and resource cleanup when session operations are initiated. When a PDO statement is executed and subsequently followed by a session_start() call, the internal state management between these two components becomes inconsistent. This misalignment occurs because the PDO row object maintains references to database resources that are not properly released before session initialization begins. The flaw specifically affects the fetch operations within PDO implementations, where the row object's destructor or cleanup methods fail to properly handle the session context, leading to memory corruption or resource conflicts that ultimately cause the Apache HTTP Server to crash.
The operational impact of this vulnerability extends beyond simple denial of service, as it can be exploited remotely to disrupt web server operations and potentially compromise system availability. Attackers can craft malicious PHP applications that leverage this flaw by first executing a PDO fetch operation and then immediately calling session_start(), causing the web server process to terminate unexpectedly. This vulnerability is particularly concerning in shared hosting environments or applications that rely heavily on database operations combined with session management, as it can be triggered through normal web application workflows without requiring special privileges or access to system resources.
From a cybersecurity perspective, this vulnerability aligns with CWE-119 Improper Access to Memory and CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization, as it involves memory management issues and race conditions between database operations and session handling. The attack vector follows ATT&CK technique T1499.004 for Denial of Service through resource exhaustion, where the vulnerability specifically targets application stability rather than network bandwidth. The vulnerability also demonstrates characteristics of T1566.001 for Initial Access through web application attacks, as it can be exploited through web-based PHP applications without requiring direct system access or specialized tools.
The primary mitigation strategy involves upgrading PHP installations to version 5.3.9 or later, where the underlying implementation has been corrected to properly handle the interaction between PDO row objects and session management. System administrators should also implement proper input validation and monitoring of session-related operations within applications to detect potential exploitation attempts. Additionally, organizations should consider implementing application firewalls or web application security controls that can identify and block malicious requests attempting to trigger this specific vulnerability pattern. The fix implemented in PHP 5.3.9 addresses the core issue by ensuring proper resource cleanup and state management between PDO operations and session initialization, preventing the memory corruption that previously led to application crashes.