Uncovering Curl's Security Vulnerabilities: What You Need to Know

3 min read
Uncovering Curl's Security Vulnerabilities: What You Need to Know

In the world of software development, security vulnerabilities are a constant concern. On October 11, 2023, the maintainers of the Curl library released an advisory regarding two security vulnerabilities, one of high severity (CVE-2023-38545) and one of low severity (CVE-2023-38546). These vulnerabilities affect both libcurl and Curl, a popular command-line tool for transferring data specified with URL syntax. In this blog, we'll delve into the details of these vulnerabilities and the potential risks they pose to users.

CVE-2023-38545: SOCKS5 Heap Buffer Overflow

The first vulnerability, CVE-2023-38545, is a high-severity issue that stems from a heap buffer overflow in the SOCKS5 proxy handshake process. When Curl is asked to pass the hostname to the SOCKS5 proxy for address resolution, a maximum length of 255 bytes is allowed. However, if the hostname exceeds this limit, Curl switches to local name resolution, unintentionally copying the excessively long hostname into the target buffer.

The significance of this vulnerability lies in the fact that an attacker could exploit it during a slow SOCKS5 handshake, potentially leading to unauthorized access or malicious activity. The developers discovered this issue had remained undetected for years, emphasizing the importance of prompt updates to address the problem.

The second vulnerability, CVE-2023-38546, is of low severity but still poses a security risk. It allows an attacker to insert cookies into a program using libcurl under specific conditions. In libcurl's API, an application can create "easy handles" for single transfers. A function called curl_easy_duphandle is provided to duplicate these handles, including their cookie-enable state.

However, a flaw in the process occurs when the source handle did not read any cookies from a specific file on disk. In this case, the cloned version of the handle inadvertently stores the file name as "none," potentially allowing an attacker to inject cookies from a file named "none" in the current directory of the program using libcurl.

The Solution: Curl Version 8.4.0

To address these vulnerabilities, the Curl library released version 8.4.0 on October 11, 2023. This release contains the necessary fixes to mitigate the risks associated with CVE-2023-38545 and CVE-2023-38546. Users and organizations are strongly encouraged to update their Curl and libcurl installations to this latest version as soon as possible to ensure the security of their systems.

For more information and detailed instructions on applying the updates, you can visit the official Curl website. Staying informed and proactive is crucial in safeguarding your digital assets, and keeping your software up to date is an essential part of that process.


Security vulnerabilities are a constant challenge in the ever-evolving landscape of software development. The recent discovery of vulnerabilities in Curl highlights the importance of staying vigilant and regularly updating software to ensure the safety of your systems and data. With the release of Curl version 8.4.0, you have the opportunity to protect your systems from potential risks associated with these security flaws. Your system's security is only as strong as its weakest link, so don't hesitate to take action to fortify your digital defenses.

Follow us on social media

Copyright © 2024 CYUN. All rights reserved.