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security: cap cloneNode/isEqualNode recursion depth - #275
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Continuing the same sweep as the calc()/:not()/:is() CSS parser fixes, this time across JS-reachable DOM methods: isEqualNode (node.isEqualNode(other)) and cloneNode (node.cloneNode(deep), also document.importNode) each recurse over a node's own Children with no depth check -- and unlike round 166's cascade/layout caps, nothing here guards a script calling one of these directly on a tree it already has, independently of whether that tree is ever rendered. Confirmed with a 10,000-deep synthetic chain (dom.AppendChild has no depth check of its own, by design) that both recurse unboundedly. Fixed with a depth parameter capped at maxDOMWalkDepth = 512, matching the HTML parser's own bound. Past the cap, isEqualNode reports false (never crashing) and cloneNode stops descending, returning a real node with an empty subtree rather than failing the whole call. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
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Summary
Continuing the same sweep as the calc()/:not()/:is() CSS parser fixes (#273/#274), this time across JS-reachable DOM methods:
isEqualNode(node.isEqualNode(other)) andcloneNode(node.cloneNode(deep), alsodocument.importNode) each recurse over a node's ownChildrenwith no depth check — and unlike round 166's cascade/layout caps, nothing here guards a script calling one of these directly on a tree it already has, independently of whether that tree is ever rendered.Confirmed with a 10,000-deep synthetic chain (
dom.AppendChildhas no depth check of its own, by design) that both recurse unboundedly. Fixed with a depth parameter capped atmaxDOMWalkDepth = 512, matching the HTML parser's own bound. Past the cap,isEqualNodereportsfalse(never crashing) andcloneNodestops descending, returning a real node with an empty subtree rather than failing the whole call.Test plan
go build ./...go test ./...(all packages pass)js/dom_test.go:TestIsEqualNodeDoesNotCrashOnPathologicallyDeepTree,TestIsEqualNodeDeepMismatchPastCapIsNotEqual,TestCloneNodeDoesNotCrashOnPathologicallyDeepTreejspackage coverage unaffected (95.9% baseline)🤖 Generated with Claude Code