Deno is a JavaScript, TypeScript, and WebAssembly runtime. Starting in version 1.35.1 and prior to version 1.36.3, a vulnerability in Denos Node.js compatibility runtime allows for cross-session data contamination during simultaneous asynchronous reads from Node.js streams sourced from sockets or files. The issue arises from the re-use of a global buffer (BUF) in stream_wrap.ts used as a performance optimization to limit allocations during these asynchronous read operations. This can lead to data intended for one session being received by another session, potentially resulting in data corruption and unexpected behavior. This affects all users of Deno that use the node.js compatibility layer for network communication or other streams, including packages that may require node.js libraries indirectly. Version 1.36.3 contains a patch for this issue.
The product does not sufficiently enforce boundaries between the states of different sessions, causing data to be provided to, or used by, the wrong session.
Data can “bleed” from one session to another through member variables of singleton objects, such as Servlets, and objects from a shared pool. In the case of Servlets, developers sometimes do not understand that, unless a Servlet implements the SingleThreadModel interface, the Servlet is a singleton; there is only one instance of the Servlet, and that single instance is used and re-used to handle multiple requests that are processed simultaneously by different threads. A common result is that developers use Servlet member fields in such a way that one user may inadvertently see another user’s data. In other words, storing user data in Servlet member fields introduces a data access race condition.