gchq/CyberChef · error · OperationError

Negative values cannot be represented as VarInt

Error message

Negative values cannot be represented as VarInt

What it means

Thrown by 'VarInt Encode' when BigInt(input) parses successfully but the value is negative. VarInt (protobuf-style) encodes unsigned integers only, so negative numbers have no valid encoding.

Source

Thrown at src/core/operations/VarIntEncode.mjs:40

        this.name = "VarInt Encode";
        this.module = "Default";
        this.description = "Encodes a Vn integer as a VarInt. VarInt is an efficient way of encoding variable length integers and is commonly used with Protobuf.";
        this.infoURL = "https://developers.google.com/protocol-buffers/docs/encoding#varints";
        this.inputType = "string";
        this.outputType = "byteArray";
        this.args = [];
    }

    /**
     * @param {string} input
     * @param {Object[]} args
     * @returns {byteArray}
     */
    run(input, args) {
        try {
            if (typeof BigInt === "function") {
                let value = BigInt(input);
                if (value < 0) throw new OperationError("Negative values cannot be represented as VarInt");
                const result = [];
                while (value >= 0x80) {
                    result.push(Number(value & BigInt(0x7f)) | 0x80);
                    value >>= BigInt(7);
                }
                result.push(Number(value));
                return result;
            } else {
                return Protobuf.varIntEncode(Number(input));
            }
        } catch (err) {
            throw new OperationError(err);
        }
    }

}

export default VarIntEncode;

View on GitHub (pinned to 4290ea7539)

Solutions

1. Provide a non-negative integer string as input.
2. If you need signed values, convert to an unsigned representation (e.g. two's complement to a fixed width) before encoding.
3. Sanitise upstream output to clamp/abs negative values when semantically appropriate.

Example fix

// before
varIntEncode("-5");
// after
varIntEncode("5");

const v = BigInt(input);
if (v < 0n) throw new Error("VarInt cannot encode negative values");

function isNonNegativeBigInt(s) { try { return BigInt(s) >= 0n; } catch { return false; } }

When it happens

Trigger: Input string representing a negative integer such as '-1' or '-42'. BigInt(input) succeeds and the value < 0 check trips before the encode loop.

Common situations: Passing signed/offset data, negative timestamps, or subtracted values into an operation that expects unsigned counts/IDs.

Related errors

• ${err}
• ${err}
• Schema Error: Schema not defined
• Input Error: ${error}
• Schema ${error}

AI-assisted analysis of gchq/CyberChef@4290ea7539 (2026-08-13). Data as JSON: /api/errors/25a8f3063bc5388c. Report an issue: GitHub.