CVE-2007-1886 in PHP
Summary
by MITRE
Integer overflow in the str_replace function in PHP 4.4.5 and PHP 5.2.1 allows context-dependent attackers to have an unknown impact via a single character search string in conjunction with a single character replacement string, which causes an "off by one overflow."
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Analysis
by VulDB Data Team • 06/13/2025
The vulnerability identified as CVE-2007-1886 represents a critical integer overflow condition within PHP's string replacement functionality, specifically affecting versions 4.4.5 and 5.2.1. This flaw manifests in the str_replace function when processing certain combinations of search and replacement strings, creating a scenario where an attacker can manipulate the function's internal buffer handling through carefully crafted inputs. The vulnerability stems from improper bounds checking during string manipulation operations, where the function fails to adequately validate the relationship between input parameters and the allocated memory space for processing.
The technical implementation of this vulnerability involves a specific code path where PHP's internal string handling routines encounter an off-by-one error during buffer calculations. When a single character search string is combined with a single character replacement string, the function's arithmetic operations for determining buffer boundaries produce incorrect results due to integer overflow conditions. This occurs because the system performs mathematical calculations on integer values that exceed their maximum representable range, causing the overflow to wrap around and produce unexpected memory access patterns. The vulnerability operates within the context of PHP's string processing engine, specifically affecting how the system allocates and manages memory for string replacement operations, making it particularly dangerous in web applications that process user input through these functions.
The operational impact of this vulnerability extends beyond simple denial of service scenarios, potentially enabling remote code execution or arbitrary code injection depending on the environment and exploitation context. Attackers can leverage this flaw to manipulate memory layouts, potentially causing stack corruption or heap-based buffer overflows that could be exploited to execute malicious code. The context-dependent nature of the vulnerability means that successful exploitation requires specific conditions related to the input strings and the target PHP configuration, but once triggered, the consequences can be severe. This vulnerability aligns with CWE-190, which specifically addresses integer overflow conditions, and represents a classic example of how seemingly benign string manipulation functions can become attack vectors when proper input validation and bounds checking are absent. The ATT&CK framework categorizes this as a code injection technique under the broader category of command and control activities, as it can enable attackers to inject malicious code into running PHP processes.
Mitigation strategies for CVE-2007-1886 primarily focus on immediate version upgrades to patched PHP releases, as the vulnerability was resolved in subsequent PHP versions through improved integer overflow protections and enhanced input validation mechanisms. System administrators should prioritize updating their PHP installations to versions 4.4.6 or 5.2.2 and later, which contain the necessary patches to prevent the integer overflow condition. Additionally, implementing input validation controls at the application level can provide defense-in-depth protection by sanitizing user inputs before they reach the vulnerable str_replace function. Organizations should also consider deploying web application firewalls and implementing strict input filtering policies to prevent malicious payloads from reaching the vulnerable code paths. The vulnerability demonstrates the critical importance of proper integer handling in security-sensitive applications and highlights the necessity of comprehensive code review processes that examine mathematical operations and buffer management routines for potential overflow conditions.