gchq/CyberChef · error · OperationError

Please enter a valid image file.

Error message

Please enter a valid image file.

What it means

Thrown by the Extract LSB (steganography) operation when isImage(input) returns false. The operation reads pixel RGBA data using Jimp and needs a valid image (PNG, JPEG, BMP). If the input ArrayBuffer does not match a recognized image file signature, the operation cannot proceed.

Source

Thrown at src/core/operations/ExtractLSB.mjs:73

                type: "option",
                value: ["Row", "Column"],
            },
            {
                name: "Bit",
                type: "number",
                value: 0,
            },
        ];
    }

    /**
     * @param {ArrayBuffer} input
     * @param {Object[]} args
     * @returns {byteArray}
     */
    async run(input, args) {
        if (!isImage(input))
            throw new OperationError("Please enter a valid image file.");

        const bit = 7 - args.pop(),
            pixelOrder = args.pop(),
            colours = args
                .filter((option) => option !== "")
                .map((option) => COLOUR_OPTIONS.indexOf(option)),
            parsedImage = await Jimp.read(input),
            width = parsedImage.bitmap.width,
            height = parsedImage.bitmap.height,
            rgba = parsedImage.bitmap.data;

        if (bit < 0 || bit > 7) {
            throw new OperationError(
                "Error: Bit argument must be between 0 and 7",
            );
        }

        let i,

View on GitHub (pinned to 4290ea7539)

Solutions

1. Provide a valid image file (PNG, JPEG, or BMP) as the input ArrayBuffer.
2. Verify the file is not truncated or corrupted by opening it in an image viewer first.
3. Convert unsupported formats to PNG/JPEG before feeding to this operation.
4. Ensure no upstream operation changes the data type away from ArrayBuffer.

Example fix

// before: input = <text file ArrayBuffer> -> isImage false -> error

// after: input = <PNG image ArrayBuffer>

// Verify input is an image before calling ExtractLSB
import { isImage } from '../lib/FileType.mjs';
if (!isImage(input)) {
  throw new Error('Input must be a valid image file');
}

function isValidImage(input) {
  // Delegates to CyberChef's FileType.isImage
  return isImage(input);
}

When it happens

Trigger: async run(input, args) where isImage(input) returns false at line 72. Input is expected to be an ArrayBuffer containing image bytes but either is not an image or is not a supported format.

Common situations: Feeding a non-image file (text, PDF, audio), a corrupted/truncated image, or an unsupported image format (e.g., WebP, HEIC depending on Jimp version). Also when an upstream operation outputs non-ArrayBuffer data.

Related errors

• Error: Bit argument must be between 0 and 7
• Please enter a valid image file.
• Invalid file type.
• Invalid file format.
• Invalid file type.

AI-assisted analysis of gchq/CyberChef@4290ea7539 (2026-08-13). Data as JSON: /api/errors/59112b635937c705. Report an issue: GitHub.