projectdiscovery/subfinder · error

response-size-read cannot be negative

Error message

response-size-read cannot be negative

What it means

validateOptions enforces that the response-body read size limit (response-size-read) is not negative. Negative MaxResponseBodySize is not a valid byte cap, so option validation fails before any HTTP requests are made.

Solutions

1. Provide a non-negative byte value for -response-size-read
2. Remove the flag to use the library default limit
3. If unlimited reads are intended, use the documented option for disabling the cap rather than a negative number

Example fix

// before
subfinder -d example.com -response-size-read -1024
// after
subfinder -d example.com -response-size-read 1048576

if maxBodySize < 0 {
    return fmt.Errorf("response-size-read must be >= 0, got %d", maxBodySize)
}

func validBodySize(n int) bool { return n >= 0 }

opts, err := runner.ParseOptions()
if err != nil && strings.Contains(err.Error(), "response-size-read cannot be negative") {
    // correct the flag and re-parse
}

When it happens

Trigger: Passing -response-size-read with a negative value on the CLI, or setting Options.MaxResponseBodySize < 0 in code before ParseOptions.

Common situations: Automation scripts templating sizes with values that default to -1; misunderstanding the flag as 'unlimited' by using negative numbers (unlimited is configured differently).

Understand the failure class

Background: "unknown output mode", "invalid value for flag", "expects true/false": fixing invalid flag value errors in CLI tools — this error's family across 24 libraries.

Related errors

• max-results cannot be negative
• invalid source specified in -rls flag

AI-assisted analysis of projectdiscovery/subfinder@7a0b91f0fa (2026-09-06). Data as JSON: /api/errors/0daa9871670bedaa. Report an issue: GitHub.

Appendix: source

Thrown at pkg/runner/validate.go:50

		return errors.New("threads cannot be zero")
	}
	if options.Timeout == 0 {
		return errors.New("timeout cannot be zero")
	}

	// Always remove wildcard with hostip
	if options.HostIP && !options.RemoveWildcard {
		return errors.New("hostip flag must be used with RemoveWildcard option")
	}

	// The per-source results limit cannot be negative.
	if options.MaxResults < 0 {
		return fmt.Errorf("max-results cannot be negative")
	}

	// The response body size limit cannot be negative.
	if options.MaxResponseBodySize < 0 {
		return fmt.Errorf("response-size-read cannot be negative")
	}

	if options.Match != nil {
		options.matchRegexes = make([]*regexp.Regexp, len(options.Match))
		var err error
		for i, re := range options.Match {
			if options.matchRegexes[i], err = regexp.Compile(stripRegexString(re)); err != nil {
				return errors.New("invalid value for match regex option")
			}
		}
	}
	if options.Filter != nil {
		options.filterRegexes = make([]*regexp.Regexp, len(options.Filter))
		var err error
		for i, re := range options.Filter {
			if options.filterRegexes[i], err = regexp.Compile(stripRegexString(re)); err != nil {
				return errors.New("invalid value for filter regex option")
			}

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