Source: cve@mitre.org
Buffer overflow in Apache 1.2.5 and earlier allows a remote attacker to cause a denial of service with a large number of GET requests containing a large number of / characters.
Apache 1.2.5 and earlier versions are vulnerable to a buffer overflow that can be triggered remotely. An attacker can exploit this vulnerability by sending a series of crafted GET requests with an excessive number of forward slashes, leading to a denial-of-service (DoS) condition, rendering the web server unavailable. This poses a significant risk to organizations relying on these outdated Apache versions.
Step 1: Payload Delivery: The attacker crafts a GET request. The request's URL contains a very long string of forward slashes (e.g., / repeated many times).
Step 2: Request Reception: The vulnerable Apache server receives the malicious GET request.
Step 3: URL Parsing: The server's URL parsing routines attempt to process the URL, including the excessively long path.
Step 4: Buffer Overflow: The long URL path, exceeding the allocated buffer size, overwrites adjacent memory locations within the server's process space. This is a buffer overflow.
Step 5: Denial of Service: The memory corruption caused by the overflow leads to a crash of the Apache process, resulting in a denial-of-service (DoS). The server becomes unresponsive to further requests.
The vulnerability lies within Apache's handling of overly long URLs. Specifically, the code responsible for parsing and processing the URL path fails to properly validate the length of the input. When a GET request is received with a URL containing an extremely long string of forward slashes ('/'), the server attempts to store this oversized string in a fixed-size buffer. This leads to a buffer overflow, where the excess data overwrites adjacent memory locations. This memory corruption can cause the Apache process to crash, resulting in a denial-of-service. The root cause is a lack of bounds checking on the URL path length before copying it into a fixed-size buffer. The specific function or logic flaw is likely within the URL parsing and processing routines, where the excessive number of '/' characters overwhelms the allocated memory.
This vulnerability is associated with older Apache versions. While specific APT groups may not be actively targeting this specific CVE, any threat actor could exploit it due to its ease of exploitation and the potential for widespread impact. It is unlikely to be in the CISA KEV as the versions are so old. However, if a critical system is running a vulnerable version, it could be a target.
Network Intrusion Detection Systems (NIDS): Monitor for unusually long URLs containing a high density of forward slashes in HTTP GET requests. Signature-based detection can be implemented to identify known exploit patterns.
Web Application Firewalls (WAFs): Configure WAFs to block requests with excessively long URLs or a high number of forward slashes.
Log Analysis: Analyze Apache access logs for suspicious activity, such as a sudden increase in requests with extremely long URLs, followed by server errors or crashes. Look for patterns in the user agent strings as well.
Host-based Intrusion Detection Systems (HIDS): Monitor system logs for Apache process crashes or unexpected behavior.
Upgrade Apache: The primary and most effective remediation is to upgrade to a patched version of Apache (1.2.6 or later). This is the most critical step.
Web Application Firewall (WAF): Implement a WAF to filter malicious requests, including those with excessively long URLs or a high number of forward slashes.
Input Validation: Ensure that all input, including URL paths, is properly validated to prevent buffer overflows. This is primarily handled by the updated Apache versions.
Regular Security Audits: Conduct regular security audits and penetration testing to identify and address vulnerabilities.
Disable Unnecessary Modules: Disable any Apache modules that are not required to reduce the attack surface.