A heap use-after-free flaw was found in curl versions from 7.59.0 through 7.61.1 in the code related to closing an easy handle. When closing and cleaning up an 'easy' handle in the `Curl_close()` func

The heap use-after-free vulnerability in cURL allows an attacker to potentially trigger a crash or, more critically, execute arbitrary code. The specific impact depends on how cURL is integrated into the application using it. If cURL is used to fetch data from an untrusted source, a malicious server could craft a response that triggers the vulnerability during the cleanup process. This could lead to a denial of service, preventing the application from functioning correctly. In more complex scenarios, an attacker might be able to overwrite memory and gain control of the application's execution flow, leading to remote code execution. The severity is rated as medium due to the potential for code execution, although exploitation may require specific conditions and attacker interaction.

Applications and systems that rely on cURL to fetch data from external sources are at risk. This includes web servers, automation scripts, and any software that uses cURL for network communication. Systems running older versions of cURL (7.59.0 - 7.61.1) are particularly vulnerable, especially those handling untrusted data.

• linux / server:

ps aux | grep curl

• linux / server:

journalctl -u curl | grep -i error

• generic web:

curl -I https://example.com/curl_endpoint | grep Server

• generic web:

curl -I https://example.com/curl_endpoint | grep cURL/

1. 2018-10-31Disclosure

   disclosure

1. Reserviert2018-09-11
2. Veröffentlicht2018-10-31
3. Geändert2026-04-16

The primary mitigation for CVE-2018-16840 is to upgrade to cURL version 7.62.0 or later, which contains the fix for this vulnerability. If upgrading is not immediately feasible, consider implementing temporary workarounds. One approach is to carefully validate the data received from external sources before passing it to cURL. This can help prevent malicious data from triggering the vulnerability. Additionally, consider using a Web Application Firewall (WAF) or proxy server to filter potentially malicious requests. While not a direct fix, these measures can reduce the attack surface. There are no specific Sigma or YARA rules readily available for this vulnerability, but monitoring memory access patterns related to cURL's easy handle cleanup could be a proactive detection strategy.