CVE-2008-7068 in PHP
Summary
by MITRE
The dba_replace function in PHP 5.2.6 and 4.x allows context-dependent attackers to cause a denial of service (file truncation) via a key with the NULL byte. NOTE: this might only be a vulnerability in limited circumstances in which the attacker can modify or add database entries but does not have permissions to truncate the file.
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Analysis
by VulDB Data Team • 08/26/2019
The vulnerability identified as CVE-2008-7068 represents a context-dependent denial of service flaw within PHP's database abstraction layer, specifically affecting the dba_replace function in PHP versions 5.2.6 and 4.x series. This vulnerability stems from insufficient input validation when processing database keys that contain NULL byte characters, creating a potential vector for attackers to manipulate database file contents. The flaw operates at the intersection of database management and input sanitization, where the application fails to properly handle null-terminated strings in database key parameters.
The technical implementation of this vulnerability exploits the fundamental behavior of string handling in C-based systems where NULL bytes are used to terminate strings. When the dba_replace function processes a key containing a NULL byte, the function's internal string processing routines interpret the NULL byte as a string terminator, effectively truncating the key at that point. This truncation can result in the replacement of database entries with modified keys or potentially cause database corruption when the function attempts to write to the database file. The vulnerability demonstrates a classic buffer handling issue where improper input validation leads to unexpected behavior in the underlying database operations.
From an operational impact perspective, this vulnerability creates a significant risk for applications that rely on PHP's database abstraction layer for data management. The denial of service condition manifests as file truncation, which can lead to data loss, corrupted database entries, or complete unavailability of database operations. While the vulnerability requires specific conditions to be exploited, including the ability to modify or add database entries, it represents a serious concern for applications where database integrity is paramount. The limited scope of exploitation means that attackers must already have some level of database write permissions, but this still constitutes a meaningful threat vector in environments where privilege separation is not strictly enforced.
The vulnerability aligns with CWE-121, which addresses buffer overflow conditions, and demonstrates the importance of proper input validation in database operations. From an ATT&CK framework perspective, this vulnerability could be leveraged as part of a broader attack chain under the T1499 category for network disruption, potentially leading to more severe consequences when combined with other exploitation techniques. The impact is particularly concerning in web applications where database interactions are frequent and where the vulnerability could be exploited through user input that gets processed through the affected PHP functions.
Mitigation strategies should focus on implementing comprehensive input validation for all database key parameters, specifically filtering or rejecting keys containing NULL bytes before they reach the dba_replace function. Application developers should also consider upgrading to patched versions of PHP where this vulnerability has been addressed, as well as implementing proper database access controls to limit the scope of potential exploitation. Additionally, monitoring and logging mechanisms should be enhanced to detect unusual database modification patterns that might indicate exploitation attempts. The vulnerability underscores the critical importance of secure coding practices in database interaction functions and the necessity of thorough testing for edge cases in string handling operations.