XTLS/Xray-core · error

Invalid hex string

Error message

Invalid hex string

What it means

Thrown by ParseNoise when a noise entry of type "hex" has a packet value that is not valid hexadecimal. The raw string is passed straight to hex.DecodeString and any error (odd length, non-hex characters) is wrapped with this message. Decoding happens at config build time, before any traffic flows.

Source

Thrown at infra/conf/freedom.go:221

		min, max, err := ParseRangeString(noise.Packet)
		if err != nil {
			return nil, errors.New("invalid value for rand Length").Base(err)
		}
		NConfig.LengthMin = uint64(min)
		NConfig.LengthMax = uint64(max)
		if NConfig.LengthMin == 0 {
			return nil, errors.New("rand lengthMin or lengthMax cannot be 0")
		}

	case "str":
		// user input string
		NConfig.Packet = []byte(noise.Packet)

	case "hex":
		// user input hex
		NConfig.Packet, err = hex.DecodeString(noise.Packet)
		if err != nil {
			return nil, errors.New("Invalid hex string").Base(err)
		}

	case "base64":
		// user input base64
		NConfig.Packet, err = base64.RawURLEncoding.DecodeString(strings.NewReplacer("+", "-", "/", "_", "=", "").Replace(noise.Packet))
		if err != nil {
			return nil, errors.New("Invalid base64 string").Base(err)
		}

	default:
		return nil, errors.New("Invalid packet, only rand/str/hex/base64 are supported")
	}

	if noise.Delay != nil {
		NConfig.DelayMin = uint64(noise.Delay.From)
		NConfig.DelayMax = uint64(noise.Delay.To)
	}
	switch strings.ToLower(noise.ApplyTo) {

View on GitHub (pinned to 7d214f8b09)

Solutions

1. Provide an even-length hex string without prefix or separators, e.g. "deadbeef".
2. Strip "0x" prefixes and whitespace before embedding.
3. If the payload is not hex, switch the type to "base64" or "str".

Example fix

// before
{"type": "hex", "packet": "0xdeadbeef"}

// after
{"type": "hex", "packet": "deadbeef"}

if noise.Type == "hex" {
    if _, err := hex.DecodeString(noise.Packet); err != nil {
        return fmt.Errorf("noise packet is not valid hex (even length, no 0x prefix): %w", err)
    }
}

When it happens

Trigger: {"type": "hex", "packet": "zz"} or "abc" (odd number of digits) or a string with 0x prefix. hex.DecodeString fails and the error is chained.

Common situations: Forgetting that Go hex requires even-length strings; including a "0x" prefix; pasting base64 into a hex field; whitespace mixed in.

Related errors

• invalid value for rand Length
• Invalid base64 string
• unsupported domain strategy: {}
• Invalid PacketsFrom
• invalid redirect address: {}

AI-assisted analysis of XTLS/Xray-core@7d214f8b09 (2026-08-15). Data as JSON: /api/errors/a2cb85c2f1846fc7. Report an issue: GitHub.