CVE-1999-0107

Step 1: Request Construction: The attacker crafts an HTTP GET request. The request includes a URL path containing a large number of forward slash characters (e.g., /../../../../.../ ).

Step 2: Request Submission: The attacker sends the crafted GET request to the vulnerable Apache web server.

Step 3: Path Parsing: The Apache server receives the request and begins to parse the URL path.

Step 4: Buffer Overflow: The server's code attempts to store the excessively long URL path string in a fixed-size buffer. Due to the lack of input validation, the string exceeds the buffer's capacity, causing a buffer overflow.

Step 5: Memory Corruption: The overflow overwrites adjacent memory regions, potentially corrupting critical data structures or code execution pointers.

Step 6: Denial of Service: The corrupted memory causes the Apache server to crash, resulting in a denial-of-service (DoS) condition. The server becomes unresponsive to further requests.

The vulnerability stems from a failure to properly validate the length of the requested URL path within the Apache web server's code. Specifically, the server's code, when parsing a GET request, doesn't adequately check the size of the string containing the URL path. When a request with an extremely long URL path, filled with numerous '/' characters, is received, the server attempts to store this oversized string in a fixed-size buffer. This leads to a buffer overflow, where the data overflows the allocated memory, corrupting adjacent memory regions. This memory corruption can overwrite critical data structures, causing the server to crash and become unavailable. The root cause is a lack of bounds checking on the input string length before copying it into a fixed-size buffer. This allows for arbitrary data to be written to memory locations outside the intended buffer, leading to a crash.