CVE-2019-14809: Incorrect parsing validation in net/url

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Background

The stdlib package in Go provides a set of standard libraries for various functionalities. The net/url package is part of the stdlib and is responsible for parsing and manipulating URLs. It offers functions like url.Parse to parse URLs and extract their components. However, a vulnerability exists in the parsing validation of net/url, which allows for the acceptance of URLs with malformed hosts. This means that the Host field can have arbitrary suffixes that do not appear in the Hostname() or Port() functions. This vulnerability can lead to authorization bypasses in certain applications.

Vulnerability Detail

The vulnerability arises from the incorrect parsing validation in the net/url package. By accepting URLs with malformed hosts, an attacker can exploit this flaw to bypass authorization mechanisms in specific applications. The Host field can be manipulated to include suffixes that are not recognized by the Hostname() or Port() functions, allowing unauthorized access to restricted resources. This vulnerability can have severe consequences, compromising the security and integrity of affected applications.

go get stdlib@vgo1.25.5

Workaround

If upgrading to a fixed version of the Go stdlib package is not immediately feasible, a possible workaround is to implement additional validation checks on the parsed URL. This can involve manually verifying the host field against the expected hostname and port, disregarding any unrecognized suffixes. Here is an example of how this can be done in Go:

import (
	"net/url"
	"strings"
)

func validateURL(rawURL string) (*url.URL, error) {
	parsedURL, err := url.Parse(rawURL)
	if err != nil {
		return nil, err
	}

	expectedHost := "example.com"
	expectedPort := "8080"

	host := parsedURL.Hostname()
	port := parsedURL.Port()

	if host != expectedHost || port != expectedPort {
		return nil, errors.New("Invalid URL")
	}

	return parsedURL, nil
}

Conclusion

The incorrect parsing validation vulnerability in the net/url package of the Go stdlib can lead to authorization bypasses in certain applications. It is crucial to update the affected package to a fixed version, such as 1.11.13 or 1.12.8, or later, to mitigate this vulnerability. If immediate upgrading is not possible, implementing additional validation checks on the parsed URL can serve as a temporary workaround. For further support on vulnerability remediation, please contact DevNack.com.

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