HTTP/2 stream-dependency tree UAF

A use-after-free vulnerability exists in libcurl when an application configures an HTTP/2 stream-dependency tree via CURLOPTSTREAMDEPENDS or CURLOPTSTREAMDEPENDSE, subsequently invokes curleasyreset, and finally terminates the handle with curleasycleanup. During this final cleanup phase, libcurl...

stale proxy password leak

libcurl had a flaw that when instructed to clear proxy authentication credentials which made it not do so, leaving the old credentials around to get used for subsequent transfers that should not know nor use them...

UAF after pause in socket callback

Calling curleasypause within the event-based CURLMOPTSOCKETFUNCTION callback triggers a use-after-free vulnerability, where libcurl attempts to store a flag using a dangling struct pointer immediately after that pointer's memory has been freed...

sending old referer

A vulnerability in libcurl caused the HTTP Referer: header to persist even when explicitly cleared. While the documentation states that passing NULL to CURLOPTREFERER suppresses the header, the option failed to clear the internal state. As a result, the previous referrer string was erroneously...

PT-2026-51755

Name of the Vulnerable Software and Affected Versions libcurl affected versions not specified Description An issue exists where the HTTP Referer: header persists even after being explicitly cleared. Although passing NULL to CURLOPT REFERER is intended to suppress the header, the internal state is...

PT-2026-51743

Name of the Vulnerable Software and Affected Versions libcurl affected versions not specified Description When performing a transfer to a specific HTTP origin hostA using Digest authentication and subsequently changing the origin to a different one hostB while reusing the same handle, libcurl...

PT-2026-51756

Name of the Vulnerable Software and Affected Versions libcurl affected versions not specified Description Applications using libcurl for transfers via SCP:// or SFTP:// that utilize the CURLOPT SSH KEYFUNCTION callback may silently accept an untrusted server. This occurs when a server presents a...

PT-2026-51750

Name of the Vulnerable Software and Affected Versions libcurl affected versions not specified Description When reusing a handle for sequential transfers driven by environment-variable proxy configuration, the software fails to clear the proxy authentication state between requests. If an initial...

PT-2026-51752

Name of the Vulnerable Software and Affected Versions libcurl affected versions not specified Description A flaw exists where the software fails to clear proxy authentication credentials when instructed to do so. This results in old credentials remaining available and potentially being used for...

PT-2026-51754

Name of the Vulnerable Software and Affected Versions libcurl affected versions not specified Description An issue exists where libcurl may send request data on a new connection before enforcing certificate verification failure. This occurs when a user first connects to a legitimate HTTP/3 server...

PT-2026-51753

Name of the Vulnerable Software and Affected Versions libcurl affected versions not specified Description A use-after-free issue occurs when the curl easy pause function is called within the event-based CURLMOPT SOCKETFUNCTION callback. This leads to a situation where libcurl attempts to store a...

CVE-2026-55568

Guzzle is an extensible PHP HTTP client. Prior to 7.12.1, in certain configurations, traffic expected to be protected by TLS on the hop to the proxy is transmitted in cleartext. Proxy authentication credentials the Proxy-Authorization header, proxy userinfo in the proxy URL, or CURLOPTPROXYUSERPW...

CVE-2026-55568

Summary (CVE-2026-55568) : Guzzle’s built‑in cURL handlers (CurlHandler/CurlMultiHandler) can downgrade an https:// proxy to plaintext when using libcurl older than 7.50.2, exposing proxy credentials and the CONNECT host/port. The issue occurs if an https proxy is configured and the app runs with...

CVE-2026-55568

Guzzle is an extensible PHP HTTP client. Prior to 7.12.1, in certain configurations, traffic expected to be protected by TLS on the hop to the proxy is transmitted in cleartext. Proxy authentication credentials the Proxy-Authorization header, proxy userinfo in the proxy URL, or CURLOPTPROXYUSERPW...

GHSA-WPWQ-4J6V-78M3 guzzlehttp/guzzle: Silent HTTPS-Proxy Downgrade to Cleartext

Impact The built-in cURL handlers GuzzleHttp\Handler\CurlHandler and GuzzleHttp\Handler\CurlMultiHandler, used by default whenever the PHP cURL extension is available accept an https:// proxy — a proxy reached over a TLS-encrypted connection — through the proxy request option, client-level proxy...

guzzlehttp/guzzle: Silent HTTPS-Proxy Downgrade to Cleartext

Impact The built-in cURL handlers GuzzleHttp\Handler\CurlHandler and GuzzleHttp\Handler\CurlMultiHandler, used by default whenever the PHP cURL extension is available accept an https:// proxy — a proxy reached over a TLS-encrypted connection — through the proxy request option, client-level proxy...

Silent HTTPS proxy downgrade to cleartext

Impact The built-in cURL handlers GuzzleHttp\Handler\CurlHandler and GuzzleHttp\Handler\CurlMultiHandler, used by default whenever the PHP cURL extension is available accept an https:// proxy — a proxy reached over a TLS-encrypted connection — through the proxy request option, client-level proxy...

EulerOS Virtualization 2.13.1 : curl (EulerOS-SA-2026-2368)

According to the versions of the curl packages installed, the EulerOS Virtualization installation on the remote host is affected by the following vulnerabilities : libcurl can in some circumstances reuse the wrong connection when asked to do an Negotiate-authenticated HTTP or HTTPS request. libcu...

curl: CVE-2026-11856: cross-origin Digest auth state leak

Summary: This issue is the HTTP sibling to the previously disclosed RTSP Digest auth leak. When an application uses libcurl and reuses the same easy handle for sequential transfers the documented best practice, the Digest authentication state captured from the first origin is silently sent to the...

TencentOS Server 4: curl (TSSA-2026:0345)

The version of Tencent Linux installed on the remote TencentOS Server 4 host is prior to tested version. It is, therefore, affected by multiple vulnerabilities as referenced in the TSSA-2026:0345 advisory. Package updates are available for TencentOS Server 4 that fix the following vulnerabilities...