facebook/react · error · Error

Cannot taint a ${kind} because the value is too general and

Error message

Cannot taint a ${kind} because the value is too general and not unique enough to block globally.

What it means

Beyond objects/functions (redirected to taintObjectReference) and strings/bigints/binary views (supported), taintUniqueValue refuses remaining types: booleans, numbers, symbols, undefined and null (reported as 'null'). These values are too general — a taint on e.g. the number 1 or true would block a huge share of legitimate traffic globally, so React refuses to register them.

Source

Thrown at packages/react/src/ReactTaint.js:97

  } else if (
    value instanceof TypedArrayConstructor ||
    value instanceof DataView
  ) {
    // For now, we just convert binary data to a string so that we can just use the native
    // hashing in the Map implementation. It doesn't really matter what form the string
    // take as long as it's the same when we look it up.
    // We're not too worried about collisions since this should be a high entropy value.
    TaintRegistryByteLengths.add(value.byteLength);
    entryValue = binaryToComparableString(value);
  } else {
    // $FlowFixMe[invalid-compare]
    const kind = value === null ? 'null' : typeof value;
    if (kind === 'object' || kind === 'function') {
      throw new Error(
        'taintUniqueValue cannot taint objects or functions. Try taintObjectReference instead.',
      );
    }
    throw new Error(
      'Cannot taint a ' +
        kind +
        ' because the value is too general and not unique enough to block globally.',
    );
  }
  const existingEntry = TaintRegistryValues.get(entryValue);
  if (existingEntry === undefined) {
    TaintRegistryValues.set(entryValue, {
      message,
      count: 1,
    });
  } else {
    existingEntry.count++;
  }
  if (finalizationRegistry !== null) {
    finalizationRegistry.register(lifetime, entryValue);
  }
}

View on GitHub (pinned to eafeac097b)

Solutions

1. Taint a higher-entropy representation instead: convert the number to a sufficiently unique string (e.g. a long random token, not the integer ID)
2. Taint the container object with taintObjectReference(message, holder)
3. Skip tainting low-entropy fields; only unique values (tokens, hashes) belong in taintUniqueValue

Example fix

// before
taintUniqueValue(msg, lifetime, user.pinCode); // number -> throws

// after
taintObjectReference(msg, user);
// or taint the unguessable token only:
taintUniqueValue(msg, lifetime, user.sessionToken); // string

// Only taint value types the registry supports
const SUPPORTED = ['string', 'bigint'];
function taintChecked(message: string, lifetime: object, value: unknown) {
  if (value instanceof DataView || ArrayBuffer.isView(value)) {
    taintUniqueValue(message, lifetime, value);
  } else if (typeof value === 'string' || typeof value === 'bigint') {
    taintUniqueValue(message, lifetime, value);
  } else if (value != null && typeof value === 'object') {
    taintObjectReference(message, value);
  } else {
    console.warn('Skipping untaintable low-entropy value:', typeof value);
  }
}

const isUniqueTaintable = (v: unknown): v is string | bigint | $ArrayBufferView =>
  typeof v === 'string' || typeof v === 'bigint' || v instanceof DataView || ArrayBuffer.isView(v);

When it happens

Trigger: Calling taintUniqueValue(message, lifetime, true), taintUniqueValue(message, lifetime, 42), or passing a symbol/undefined as the value.

Common situations: Attempting to taint a numeric ID or a boolean flag from a database row; defensive-security code that loops over every property of a secret object and taints each value indiscriminately.

Related errors

• To taint a value, a lifetime must be defined by passing an o
• taintUniqueValue cannot taint objects or functions. Try tain
• Only objects or functions can be passed to taintObjectRefere
• Only objects or functions can be passed to taintObjectRefere
• Invalid tag: ${tag}

AI-assisted analysis of facebook/react@eafeac097b (2026-08-21). Data as JSON: /api/errors/d236f6cda16810bc. Report an issue: GitHub.