CVE-2022-35922 in Rust-WebSocket
Summary
by MITRE • 08/02/2022
Rust-WebSocket is a WebSocket (RFC6455) library written in Rust. In versions prior to 0.26.5 untrusted websocket connections can cause an out-of-memory (OOM) process abort in a client or a server. The root cause of the issue is during dataframe parsing. Affected versions would allocate a buffer based on the declared dataframe size, which may come from an untrusted source. When `Vec::with_capacity` fails to allocate, the default Rust allocator will abort the current process, killing all threads. This affects only sync (non-Tokio) implementation. Async version also does not limit memory, but does not use `with_capacity`, so DoS can happen only when bytes for oversized dataframe or message actually got delivered by the attacker. The crashes are fixed in version 0.26.5 by imposing default dataframe size limits. Affected users are advised to update to this version. Users unable to upgrade are advised to filter websocket traffic externally or to only accept trusted traffic.
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Analysis
by VulDB Data Team • 08/02/2022
The vulnerability described in CVE-2022-35922 represents a critical memory exhaustion issue within the Rust-WebSocket library affecting versions prior to 0.26.5. This flaw manifests as a denial of service condition that can lead to complete process termination through out-of-memory scenarios. The vulnerability specifically impacts the synchronous implementation of the WebSocket library while the asynchronous version remains partially unaffected due to different memory allocation patterns. The root cause lies in the dataframe parsing mechanism where the library allocates memory buffers based on size declarations contained within WebSocket dataframes, without proper validation of these size parameters.
The technical implementation of this vulnerability stems from the use of Vec::with_capacity function during dataframe processing. When processing untrusted WebSocket connections, the library accepts dataframe size declarations directly from incoming data without implementing reasonable bounds checking. This allows malicious actors to craft specially crafted dataframes with extraordinarily large size values that would cause the underlying Rust allocator to fail during memory allocation. The default Rust allocator behavior in such failure conditions is to immediately abort the entire process, terminating all active threads and resulting in complete service disruption. This particular flaw aligns with CWE-122, Heap-based Buffer Overflow, and CWE-400, Uncontrolled Resource Consumption, as it represents both a memory allocation failure and an unbounded resource consumption issue.
The operational impact of this vulnerability extends beyond simple service disruption to encompass complete system availability compromise. An attacker exploiting this vulnerability can cause immediate process termination through a single malicious WebSocket connection, making it particularly dangerous in production environments where WebSocket services handle multiple concurrent connections. The vulnerability affects both client and server implementations of the library, meaning that any system using the affected version could be compromised. The memory exhaustion occurs during the parsing phase rather than during data transmission, making it difficult to detect through standard network monitoring tools as the attack appears to originate from legitimate WebSocket protocol processing.
The mitigation strategy implemented in version 0.26.5 involves the introduction of default dataframe size limits that prevent the allocation of excessively large memory buffers. This approach addresses the core issue by establishing reasonable boundaries on memory allocation based on the declared dataframe sizes. The fix effectively transforms an exploitable vulnerability into a controlled resource management scenario where large dataframes are rejected rather than processed. Organizations unable to upgrade immediately should implement external traffic filtering mechanisms or restrict WebSocket connections to trusted sources only. This vulnerability demonstrates the importance of input validation in network libraries and aligns with ATT&CK technique T1499.004, Uninstall/Remove Tool, as it represents a method of service disruption through resource exhaustion rather than direct exploitation of code execution vulnerabilities. The fix also reflects industry best practices for memory safety and resource management in network protocol implementations, particularly in environments where untrusted network data must be processed.