CVE-2018-1303 in HTTP Server
Summary
by MITRE
A specially crafted HTTP request header could have crashed the Apache HTTP Server prior to version 2.4.30 due to an out of bound read while preparing data to be cached in shared memory. It could be used as a Denial of Service attack against users of mod_cache_socache. The vulnerability is considered as low risk since mod_cache_socache is not widely used, mod_cache_disk is not concerned by this vulnerability.
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Analysis
by VulDB Data Team • 02/24/2023
The vulnerability identified as CVE-2018-1303 represents a critical denial of service flaw within the Apache HTTP Server software ecosystem. This issue specifically affects versions prior to 2.4.30 and stems from improper handling of HTTP request headers during the caching process. The flaw manifests when the server attempts to prepare data for storage in shared memory through the mod_cache_socache module, creating a scenario where malformed input can trigger unexpected behavior. The root cause lies in an out-of-bounds memory read operation that occurs during header processing, fundamentally compromising the server's stability and operational integrity.
The technical implementation of this vulnerability involves a precise sequence of memory operations that fail to properly validate input boundaries. When an attacker crafts a malicious HTTP request header designed to exploit the shared memory caching mechanism, the Apache server processes this input through the mod_cache_socache module without adequate boundary checks. This leads to an out-of-bounds read condition where the software attempts to access memory locations beyond the allocated buffer space, resulting in a crash of the httpd process. The vulnerability operates at the application layer and requires specific module configurations to be exploitable, making it less prevalent than other classes of vulnerabilities.
From an operational perspective, this vulnerability presents a significant risk to systems that actively utilize the mod_cache_socache module for performance optimization. The denial of service impact is severe as it completely interrupts web service availability, potentially affecting thousands of concurrent users depending on the server configuration. The low risk classification stems from the limited adoption of mod_cache_socache across production environments, with most deployments relying on the more commonly used mod_cache_disk module which remains unaffected by this particular flaw. Security practitioners must consider the specific module configurations when assessing risk exposure and implementing remediation strategies.
The vulnerability aligns with CWE-125, which describes out-of-bounds read conditions that occur when software attempts to access memory beyond the boundaries of allocated buffers. This categorization places the flaw within the broader context of memory safety issues that have historically plagued software systems. From an adversarial perspective, this vulnerability maps to the ATT&CK technique T1499.004, which involves network denial of service attacks through resource exhaustion or system instability. The attack vector requires minimal sophistication and can be executed with readily available tools, making it attractive to threat actors seeking to disrupt web services. Organizations should prioritize patching affected systems to prevent exploitation, while monitoring for anomalous traffic patterns that might indicate attempted exploitation of this vulnerability.
Mitigation strategies should focus on immediate deployment of Apache HTTP Server version 2.4.30 or later, which includes the necessary code modifications to prevent the out-of-bounds read condition. System administrators should also consider disabling mod_cache_socache if it is not essential for their operational requirements, thereby eliminating the attack surface entirely. Network-level protections such as rate limiting and intrusion detection systems can provide additional defense-in-depth measures, though they cannot prevent the vulnerability from manifesting in patched systems. Regular security assessments should verify that no legacy configurations remain that could expose the system to this specific vulnerability.