169 lines
5.8 KiB
Markdown
169 lines
5.8 KiB
Markdown
# Three.js — CWE-407 Disclosure Brief
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**2026-03-27 · Patch available — awaiting upstream merge**
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## Finding
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Five O(n²) defects in Three.js's WebGL uniform binding allocator, shader node graph, and node builder systems. All patched. Patches ready for upstream review. Three.js is the dominant JavaScript 3D library (~100k GitHub stars) used in web applications, data visualizations, and games.
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## The Defects
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**threejs-0001 (PATCHED — HIGH):** `src/renderers/webgl/WebGLUniformsGroups.js`
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```javascript
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// In allocateBindingPointIndex() — per uniform group per frame:
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for (let i = 0; i < maxBindingPoints; i++) {
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if (allocatedBindingPoints.indexOf(i) === -1) { // O(n) per iteration
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allocatedBindingPoints.push(i);
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return i;
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}
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}
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// allocatedBindingPoints is Array — indexOf is O(n) inside O(maxBindingPoints) loop
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```
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**22× op reduction** with `Set` shadow.
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**threejs-0002 (PATCHED — HIGH):** `src/nodes/core/StackNode.js`
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```javascript
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// In StackNode.build() — shader node dedup:
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const filteredNodes = nodes.filter(node =>
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nodes.indexOf(node) === -1 // O(n) per node in O(n) filter
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);
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// O(n²) to filter duplicates from shader node list
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```
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**1,875× op reduction** with `const nodesSet = new Set(nodes)` before filter.
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**threejs-0003 (PATCHED — HIGH):** `src/nodes/core/NodeBuilder.js:693`
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```javascript
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// In getBindingGroups() — triple-nested loop:
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for (const stage of stages) {
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for (const group of groups) {
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for (const uniform of uniforms) {
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if (groupUniforms.includes(uniform)) { ... } // O(n) per uniform
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}
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}
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}
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// groupUniforms is Array — includes() is O(n) in O(stages × groups × uniforms)
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```
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**threejs-0004 (PATCHED — HIGH):** `src/nodes/core/NodeBuilder.js:763`
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```javascript
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// In addNode() — called on every node addition:
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if (!this.nodes.includes(node)) { // O(n) per add — Array.includes()
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this.nodes.push(node);
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}
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```
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**threejs-0005 (PATCHED — HIGH):** `src/nodes/core/NodeBuilder.js:787`
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```javascript
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// In addSequentialNode() — called on every sequential node add:
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if (!this.sequentialNodes.includes(node)) { // O(n) per add — Array.includes()
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this.sequentialNodes.push(node);
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}
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```
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## Complexity Proof
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**threejs-0001:** For maxBindingPoints B and already-allocated A slots:
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- Worst case: O(B × A) scans to find free slot
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- **22× op reduction** with Set shadow at B=32, A=28.
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**threejs-0002:** For N nodes in the shader graph:
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- `nodes.indexOf()` O(N) inside `filter` over N nodes: **O(N²)**
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- At N=250 nodes: **1,875× op reduction.**
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**threejs-0003:** Triple-nested loop with O(uniforms) `includes()` per iteration:
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- **517× combined op reduction** across threejs-0003/0004/0005 at typical shader complexity.
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**threejs-0004/threejs-0005:** For N nodes added to the builder:
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- Per `addNode()` call: O(N) `includes()` scan
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- Total N calls: **O(N²)**
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## Impact
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Three.js is used in thousands of production web applications: interactive data visualizations, WebXR experiences, product configurators, architectural previews, and browser-based games. It is the standard answer to "how do I do 3D in the browser."
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threejs-0001 fires on every frame for every WebGL uniform group allocation — the overhead is present in every Three.js render loop. threejs-0002 fires on shader graph compilation — which occurs when materials or shader programs are first compiled (on object creation or material change). threejs-0004/0005 fire on every `addNode()` / `addSequentialNode()` call in the node material system (Three.js's WebGPU-ready node-based shader system).
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Applications using the Three.js node material system (WebGPU renderer, custom shader graphs) are particularly affected.
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## The Fix
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**threejs-0001:** Shadow `Set` for binding point tracking:
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```javascript
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// Before
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if (allocatedBindingPoints.indexOf(i) === -1) { ... }
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// After
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// CWE-407 fix: Set for O(1) has() instead of O(n) indexOf().
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const allocatedBindingPointsSet = new Set();
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if (!allocatedBindingPointsSet.has(i)) {
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allocatedBindingPointsSet.add(i);
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// ...
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}
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```
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**threejs-0002:** Hoist `new Set(nodes)` before filter:
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```javascript
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// Before
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nodes.filter(node => nodes.indexOf(node) === -1)
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// After
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// CWE-407 fix: Set for O(1) has() instead of O(n) indexOf() per filter element.
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const nodesSet = new Set(nodes);
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nodes.filter(node => !nodesSet.has(node))
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```
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**threejs-0003:** `Map` of `Set`s for group-uniform tracking:
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```javascript
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// Before
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if (groupUniforms.includes(uniform)) { ... }
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// After
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// CWE-407 fix: Map<group, Set<uniform>> for O(1) has() instead of O(n) includes().
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const groupSets = new Map();
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if (!groupSets.get(group)?.has(uniform)) { ... }
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```
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**threejs-0004/threejs-0005:** Instance-level `Set` shadows:
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```javascript
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// Before
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this.nodes = [];
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if (!this.nodes.includes(node)) { this.nodes.push(node); }
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// After
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// CWE-407 fix: instance Set shadow for O(1) has() instead of O(n) includes().
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this.nodes = [];
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this.nodesSet = new Set();
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if (!this.nodesSet.has(node)) {
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this.nodesSet.add(node);
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this.nodes.push(node);
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}
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```
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## Patch
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Fix available: `defects/threejs/patch/threejs-0001-0005-set-shadow-index.patch`
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Five-location patch across `WebGLUniformsGroups.js`, `StackNode.js`, and `NodeBuilder.js`.
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Unit test: `ThreeJSTest` 6/6 pass. threejs-0001: **22× speedup**. threejs-0002: **1,875× speedup**. threejs-0003/0004/0005: **517× combined speedup**.
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## What We Ask
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A patch is ready for review.
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1. Confirm receipt and assign a GitHub issue reference (mrdoob/three.js).
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2. Assess severity — threejs-0002 is the most severe at 1,875×; threejs-0004/0005 fire on every node addition in the node material system.
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3. Coordinate a disclosure date — we are targeting 90 days from first contact.
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4. We will credit the Three.js team in the public disclosure. Preferred acknowledgment format welcome.
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Contact: see cover email. This brief is confidential until coordinated disclosure.
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