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fix: don't recurse into nested index source maps - #25
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Per ECMA-426, the "map" of an index source map section is a regular source map; nested index maps are not allowed. The decoder nevertheless recursed into them via decode() <-> decodeIndexMap() without any depth limit, so a deeply nested (~8000 levels, ~0.5 MiB) map overflowed the call stack with a RangeError. Nested maps were also decoded incorrectly, as the inner call reset the outer section's generated offset to 0:0. decodeIndexMap() now decodes sections with decodeMap() directly and skips sections that are index maps themselves in lax mode, or throws in strict mode.
OrKoN
approved these changes
Oct 13, 2026
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Per ECMA-426, the "map" of an index source map section is a regular source map; nested index maps are not allowed. The decoder nevertheless recursed into them via decode() <-> decodeIndexMap() without any depth limit, so a deeply nested (~8000 levels, ~0.5 MiB) map overflowed the call stack with a RangeError. Nested maps were also decoded incorrectly, as the inner call reset the outer section's generated offset to 0:0.
decodeIndexMap() now decodes sections with decodeMap() directly and skips sections that are index maps themselves in lax mode, or throws in strict mode.