mozilla/pdf.js · error · Error

mapBfRangeToArray - ignoring data above MAX_MAP_RANGE.

Error message

mapBfRangeToArray - ignoring data above MAX_MAP_RANGE.

What it means

Thrown by CMap.mapBfRangeToArray when the array-form bfrange (beginbfrange ... [ ... ] ... endbfrange) declares a range wider than MAX_MAP_RANGE (2^24 - 1). Same guard as the other map*Range methods but for the array-destination variant where each code maps to a listed entry.

Source

Thrown at src/core/cmap.js:257

    while (low <= high) {
      this._map[low++] = dstLow;
      // Only the last byte has to be incremented (in the normal case).
      const nextCharCode = dstLow.charCodeAt(lastByte) + 1;
      if (nextCharCode > 0xff) {
        dstLow =
          dstLow.substring(0, lastByte - 1) +
          String.fromCharCode(dstLow.charCodeAt(lastByte - 1) + 1) +
          "\x00";
        continue;
      }
      dstLow =
        dstLow.substring(0, lastByte) + String.fromCharCode(nextCharCode);
    }
  }

  mapBfRangeToArray(low, high, array) {
    if (high - low > MAX_MAP_RANGE) {
      throw new Error("mapBfRangeToArray - ignoring data above MAX_MAP_RANGE.");
    }
    const ii = array.length;
    let i = 0;
    while (low <= high && i < ii) {
      this._map[low] = array[i++];
      ++low;
    }
  }

  // This is used for both bf and cid chars.
  mapOne(src, dst) {
    this._map[src] = dst;
  }

  lookup(code) {
    return this._map[code];
  }

View on GitHub (pinned to 5903d58d58)

Solutions

Regenerate the PDF or its ToUnicode stream.
Update pdf.js.
Author CMaps with array-bfrange ranges no wider than 0xFFFFFF.
Catch FormatError/Error and degrade text extraction for that font.

Example fix

// before
const cmap = await CMapFactory.create({ encoding, fetchBuiltInCMap, useCMap });

// after
let cmap;
try {
  cmap = await CMapFactory.create({ encoding, fetchBuiltInCMap, useCMap });
} catch (e) {
  if (/MAX_MAP_RANGE/.test(e.message)) {
    console.warn('Oversized CMap bf-array range, skipping', e);
    cmap = null;
  } else throw e;
}

Defensive patterns

Strategy: try-catch

Try / catch

try {
  cmap = await CMapFactory.create({ encoding, fetchBuiltInCMap, useCMap });
} catch (e) {
  if (/MAX_MAP_RANGE/.test(e.message)) {
    console.warn('Oversized bf-array range in CMap, skipping', e);
    cmap = null;
  } else {
    throw e;
  }
}

Prevention

Sanitize untrusted PDFs before rendering.
Keep pdf.js updated.
When authoring array-form bfrange CMaps, keep each range <= 0xFFFFFF.
Validate generated CMaps with a round-trip parse before shipping.

When it happens

Trigger: Parsing a CMap where a beginbfrange line uses the [<low> <high> [<d0> <d1> ...]] array form and high - low > 0xFFFFFF.

Common situations: Corrupt or hand-crafted ToUnicode CMap using the array bfrange form with an absurdly wide range; malicious PDF.

Related errors

AI-assisted analysis of mozilla/pdf.js@5903d58d58 (2026-08-13). Data as JSON: /api/errors/f8540a16f3943bb7. Report an issue: GitHub.