CVE-2018-1000518 in Websockets
Summary
by MITRE
aaugustin websockets version 4 contains a CWE-409: Improper Handling of Highly Compressed Data (Data Amplification) vulnerability in Servers and clients, unless configured with compression=None that can result in Denial of Service by memory exhaustion. This attack appear to be exploitable via Sending a specially crafted frame on an established connection. This vulnerability appears to have been fixed in 5.
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Analysis
by VulDB Data Team • 03/28/2023
The vulnerability identified as CVE-2018-1000518 affects the aaugustin websockets library version 4, representing a critical security flaw categorized under CWE-409: Improper Handling of Highly Compressed Data. This weakness manifests in both server and client implementations of the websocket library, creating a significant risk for systems that rely on websocket communication protocols. The vulnerability stems from inadequate handling of compressed data streams that can be manipulated to cause excessive memory consumption during decompression processes.
The technical flaw exploits the library's compression handling mechanism where maliciously crafted websocket frames can trigger data amplification attacks. When compression is enabled, the websocket implementation processes incoming compressed data without proper bounds checking or resource allocation limits. Attackers can craft specially designed frames that appear small in size but decompress to enormous payloads, leading to memory exhaustion on the target system. This vulnerability specifically affects systems where the websocket library operates with default compression settings rather than explicitly configured compression=None parameters.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise entire system stability and availability. Memory exhaustion caused by this attack can lead to system crashes, application hangs, or complete service outages that affect legitimate users and operations. The attack vector requires only a single established connection to be effective, making it particularly dangerous as it can be exploited by unauthorized parties who have gained access to a websocket endpoint. The vulnerability's exploitation potential increases when the target system processes large volumes of websocket traffic, amplifying the impact of each malicious frame.
Systems running version 4 of the aaugustin websockets library are vulnerable to this memory exhaustion attack unless they have explicitly configured the library to disable compression using compression=None. The fix implemented in version 5 addresses this vulnerability by introducing proper bounds checking and resource management for compressed data processing. Organizations should prioritize upgrading to version 5 or later to eliminate this exposure. Additionally, implementing network-level monitoring and rate limiting for websocket connections can provide additional defense-in-depth measures against potential exploitation attempts.
This vulnerability aligns with ATT&CK technique T1499.004: Endpoint Denial of Service, which focuses on consuming system resources through malicious inputs. The CWE-409 classification specifically addresses the improper handling of compressed data that can lead to resource exhaustion, making this a prime example of how compression algorithms can be weaponized in denial of service attacks. The vulnerability demonstrates the importance of proper input validation and resource management in network protocols, particularly those handling binary data streams. Security teams should also consider implementing automated scanning tools to identify systems running vulnerable versions of the library and ensure comprehensive patch management processes are in place to prevent similar issues in other components of their websocket infrastructure.