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node:zlib: zstd ignores an ArrayBuffer dictionary and does not reject a dictionary of a wrong type (Node v26.10.0 does) #44258
Description
What happens
The zstd classes of node:zlib ignore a dictionary option that is not a Buffer, TypedArray or DataView. Node v26.10.0 uses an ArrayBuffer dictionary and throws ERR_INVALID_ARG_TYPE for each other type.
bun matches Node v26.3.0 here. Node changed two times after that:
- v26.7.0 accepts an
ArrayBuffer(nodejs/node#64599, "zlib: accept ArrayBuffer dictionary in Zstd"). - v26.10.0 throws for the other types (commit
5e55085bc1, "zlib: reject invalid zstd dictionaries", from nodejs/node#65867).
Reproduction
const zlib = require("node:zlib");
const dictionary = Buffer.from(
"Lorem ipsum dolor sit amet, consectetur adipiscing elit. " +
"Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.",
);
const input = Buffer.alloc(2000, "Lorem ipsum dolor sit amet, consectetur adipiscing elit. ");
console.log("view dictionary:", zlib.zstdCompressSync(input, { dictionary }).length, "bytes");
console.log("no dictionary:", zlib.zstdCompressSync(input).length, "bytes");
const arrayBuffer = dictionary.buffer.slice(dictionary.byteOffset, dictionary.byteOffset + dictionary.byteLength);
for (const [label, value] of [
["ArrayBuffer", arrayBuffer],
["string", "a string"],
["number", 42],
["null", null],
]) {
try {
const stream = zlib.createZstdCompress({ dictionary: value });
console.log(label + ":", stream._processChunk(input, zlib.constants.ZSTD_e_end).length, "bytes");
} catch (e) {
console.log(label + ": throws", e.code);
}
}Node v26.10.0:
view dictionary: 20 bytes
no dictionary: 76 bytes
ArrayBuffer: 20 bytes
string: throws ERR_INVALID_ARG_TYPE
number: throws ERR_INVALID_ARG_TYPE
null: throws ERR_INVALID_ARG_TYPE
bun 1.4.3 canary and Node v26.3.0:
view dictionary: 20 bytes
no dictionary: 76 bytes
ArrayBuffer: 76 bytes
string: 76 bytes
number: 76 bytes
null: 76 bytes
createZstdDecompress has the same difference.
Where
The Zstd constructor passes the dictionary to the native handle only when it is a view:
Lines 841 to 850 in 542f52b
The Brotli constructor in the same file already converts an ArrayBuffer and throws for the other types.
Activity
Jarred-Sumner commentedon Oct 8, 2026
Use handoff tool. GitHub issues are for user-facing issues and a user did not run into this issue