OESA-2026-1954

Node.js is a platform built on Chrome's JavaScript runtime for easily building fast, scalable network applications. Node.js uses an event-driven, non-blocking I/O model that makes it lightweight and efficient, perfect for data-intensive real-time applications that run across distributed devices.

Security Fix(es):

A flaw in Node.js HTTP request handling causes an uncaught TypeError when a request is received with a header named __proto__ and the application accesses req.headersDistinct.

When this occurs, dest["__proto__"] resolves to Object.prototype rather than undefined, causing .push() to be called on a non-array. This exception is thrown synchronously inside a property getter and cannot be intercepted by error event listeners, meaning it cannot be handled without wrapping every req.headersDistinct access in a try/catch.

• This vulnerability affects all Node.js HTTP servers on 20.x, 22.x, 24.x, and v25.x(CVE-2026-21710)

A flaw in Node.js HMAC verification uses a non-constant-time comparison when validating user-provided signatures, potentially leaking timing information proportional to the number of matching bytes. Under certain threat models where high-resolution timing measurements are possible, this behavior could be exploited as a timing oracle to infer HMAC values.

Node.js already provides timing-safe comparison primitives used elsewhere in the codebase, indicating this is an oversight rather than an intentional design decision.

This vulnerability affects 20.x, 22.x, 24.x, and 25.x.(CVE-2026-21713)

A memory leak occurs in Node.js HTTP/2 servers when a client sends WINDOW_UPDATE frames on stream 0 (connection-level) that cause the flow control window to exceed the maximum value of 2³¹-1. The server correctly sends a GOAWAY frame, but the Http2Session object is never cleaned up.

This vulnerability affects HTTP2 users on Node.js 20, 22, 24 and 25.(CVE-2026-21714)

A flaw in Node.js Permission Model filesystem enforcement leaves fs.realpathSync.native() without the required read permission checks, while all comparable filesystem functions correctly enforce them.

As a result, code running under --permission with restricted --allow-fs-read can still use fs.realpathSync.native() to check file existence, resolve symlink targets, and enumerate filesystem paths outside of permitted directories.

This vulnerability affects 20.x, 22.x, 24.x, and 25.x processes using the Permission Model where --allow-fs-read is intentionally restricted.(CVE-2026-21715)

An incomplete fix for CVE-2024-36137 leaves FileHandle.chmod() and FileHandle.chown() in the promises API without the required permission checks, while their callback-based equivalents (fs.fchmod(), fs.fchown()) were correctly patched.

As a result, code running under --permission with restricted --allow-fs-write can still use promise-based FileHandle methods to modify file permissions and ownership on already-open file descriptors, bypassing the intended write restrictions.

This vulnerability affects 20.x, 22.x, 24.x, and 25.x processes using the Permission Model where --allow-fs-write is intentionally restricted.(CVE-2026-21716)

A flaw in V8's string hashing mechanism causes integer-like strings to be hashed to their numeric value, making hash collisions trivially predictable. By crafting a request that causes many such collisions in V8's internal string table, an attacker can significantly degrade performance of the Node.js process.

The most common trigger is any endpoint that calls JSON.parse() on attacker-controlled input, as JSON parsing automatically internalizes short strings into the affected hash table.

This vulnerability affects 20.x, 22.x, 24.x, and 25.x.(CVE-2026-21717)