Source: cve@mitre.org
An issue was discovered in the ws crate through 2020-09-25 for Rust. The outgoing buffer is not properly limited, leading to a remote memory-consumption attack.
A critical vulnerability exists in the ws crate for Rust, allowing for a remote memory-consumption attack. Attackers can exploit this flaw to exhaust server resources, leading to a denial-of-service (DoS) condition and potentially impacting service availability. This vulnerability could be leveraged to disrupt critical infrastructure or online services.
Step 1: Connection Establishment: The attacker establishes a WebSocket connection with a vulnerable server using the ws crate.
Step 2: Malicious Payload Construction: The attacker crafts a WebSocket message containing a large payload. This payload is designed to trigger excessive memory allocation on the server.
Step 3: Payload Delivery: The attacker sends the crafted WebSocket message to the server.
Step 4: Server Processing: The server, using the vulnerable ws crate, attempts to process the incoming message and write the payload to the outgoing buffer.
Step 5: Memory Allocation: Due to the lack of buffer size checks, the server allocates an excessive amount of memory to accommodate the large payload.
Step 6: Resource Exhaustion: The server's memory resources are exhausted, potentially leading to a denial-of-service condition as the server becomes unresponsive or crashes.
The vulnerability stems from a lack of proper buffer size limitations when handling outgoing WebSocket messages within the ws crate. Specifically, the code fails to adequately restrict the size of the outgoing buffer, allowing an attacker to craft malicious WebSocket messages that, when processed, consume excessive memory on the server. This leads to a memory exhaustion condition. The root cause is a missing or insufficient check on the size of the data being written to the outgoing buffer before the write operation occurs. This allows an attacker to send a large amount of data, causing the server to allocate an excessive amount of memory, eventually leading to a denial of service. The vulnerability is a form of resource exhaustion attack.
While no specific APT groups are directly linked to this CVE, the ease of exploitation and potential impact make it attractive to various threat actors. This type of vulnerability is often exploited by actors seeking to disrupt service availability. This CVE is not listed in the CISA KEV catalog.
Monitor server resource usage (CPU, memory, disk I/O) for unusual spikes or sustained high utilization.
Analyze WebSocket traffic for unusually large message sizes or a high volume of messages from a single source.
Implement network intrusion detection systems (IDS) with rules to identify and block malicious WebSocket traffic patterns.
Examine server logs for errors related to memory allocation or resource exhaustion.
Monitor for abrupt service restarts or crashes, which could indicate a DoS attack.
Update the ws crate to a patched version (or the latest version) that addresses the buffer size limitation vulnerability.
Implement input validation to restrict the size of WebSocket messages accepted by the server.
Configure rate limiting to limit the number of WebSocket messages received from a single client within a specific time frame.
Monitor server resource usage and implement alerts to notify administrators of unusual activity.
Consider using a reverse proxy or load balancer to filter and inspect WebSocket traffic before it reaches the vulnerable server.
Implement defense-in-depth strategies, including regular security audits and penetration testing.