Authentication Bypass by Primary Weakness Affecting libcurl package, versions [7.76.0,8.20.0)
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-CONAN-LIBCURL-16340567
- published2 May 2026
- disclosed29 Apr 2026
- creditQuac Tran, Ngoc Hieu
Introduced: 29 Apr 2026
NewCVE-2026-5545 (opens in a new tab)How to fix?
Upgrade libcurl to version 8.20.0 or higher.
Overview
Affected versions of this package are vulnerable to Authentication Bypass by Primary Weakness via the reuse of HTTP Negotiate authenticated connections. An attacker can gain unauthorized access or perform actions with unintended credentials by making an authenticated HTTP(S) request after a Negotiate-authenticated one to the same host, causing the request to be sent over a connection authenticated with different credentials.
Workaround
This vulnerability can be mitigated by disabling connection reuse using the following libcurl options: set CURLOPT_FRESH_CONNECT to force a new connection for each request, limit the total number of open connections with CURLOPT_MAXCONNECTS, or limit connections per host with CURLMOPT_MAX_HOST_CONNECTIONS when using the curl_multi API.