CVE-2022-27776 refers to an insufficiently protected credentials vulnerability in fixed in cURL version 7.83.. The issue might cause authentication or cookie header data to leak when an HTTP redirect happens to the same host but another port number. This post will detail how the vulnerability works, provide a code snippet demonstrating the exploit, direct you to original references related to the issue, and discuss any further mitigation steps.

Vulnerability Overview

Curl is a popular command-line tool and library for transferring data with URLs and supports multiple protocols, including HTTP, HTTPS, FTP, and more. In versions prior to 7.83., an issue with how Curl handles HTTP redirects might cause sensitive data leakage. This occurs if an HTTP redirect points the user to the same host but another port number, and Curl would, in some cases, end up leaking authentication or cookie header data.

The vulnerability is assigned the Common Vulnerabilities and Exposures (CVE) identifier CVE-2022-27776, and it has been fixed in Curl version 7.83..

Here is a fictitious example demonstrating the exploit

1. An attacker sets up an HTTP server on the same host as a vulnerable Curl installation and listens on a different port. For example, the vulnerable Curl is running on port 80, and the attacker's server listens on port 808.

The attacker then sends the following redirect response from their server

  HTTP/1.1 302 Found

3. The victim's Curl client sends a request to the attacker's server, e.g.,

The attacker's server replies with an HTTP redirect to port 808 (as shown above).

5. The victim's Curl client follows the redirect and sends the same sensitive authentication or cookie header data to the new port (808 in this case), causing sensitive data leakage to the attacker.

- Curl Security Advisory - This is the original security advisory documenting the CVE-2022-27776 vulnerability.
- Curl GitHub Repository - The official Curl GitHub repository, where you can find patch details, commit logs, and related issues.
- Curl Changelog - The official changelog for Curl, detailing what has been fixed in each release, including version 7.83..

Mitigation and Next Steps

To address CVE-2022-27776, it is recommended that users upgrade to Curl version 7.83. or later. This updated version contains a patch that prevents the undesired leakage of sensitive authentication and cookie header data during an HTTP redirect to a different port number on the same host.

Additionally, users should always be cautious about any unsolicited redirects to different port numbers and, if possible, avoid following them. Custom applications using the Curl library should also be updated to the latest version, so they too can benefit from the security patch.


CVE-2022-27776 is an important vulnerability in Curl that might lead to sensitive data leakage during HTTP redirects. The issue has been fixed in Curl version 7.83., and it is crucial for users to upgrade to this or later versions to mitigate potential risks. By staying up to date with security updates and practicing caution when presented with potentially malicious redirects, affected users can help protect their authentication and cookie header data from being exposed.


Published on: 06/02/2022 14:15:00 UTC
Last modified on: 08/29/2022 01:15:00 UTC