curl_cffi: Redirect-based SSRF leads to internal network access in curl_cffi (with TLS impersonation bypass)

Summary curlcffi does not restrict requests to internal IP ranges, and follows redirects automatically via the underlying libcurl. Because of this, an attacker-controlled URL can redirect requests to internal services such as cloud metadata endpoints. In addition, curlcffi’s TLS impersonation...

curl: ignoring 'options' when doing connection reuse

libcurl contains a significant logic flaw in its connection pool matching mechanism. When a transfer specifies a required authentication policy—such as a specific SASL mechanism e.g., ;AUTH=GSSAPI or a restricted set of SSH authentication types CURLOPTSSHAUTHTYPES—libcurl fails to verify these...

curl: # SCURLOPT_SSH_KNOWNHOSTS and host fingerprint pins are silently bypassed when an SSH connection is reused from the connection pool

Product libcurl all versions, all platforms, compiled with USESSH Protocols affected: sftp://, scp:// --- Summary libcurl's connection pool reuse logic for SSH-based protocols SFTP, SCP contains a security gap that allows a transfer's server-verification policy to be completely ignored. When an...

curl: Bypassing Strict SSH Server Verification via Connection Pool Reuse in libcurl

Summary There is a logic flaw in how libcurl manages its connection pool for SSH protocols SFTP/SCP. When evaluating an existing connection for reuse, sshconfigmatches in lib/url.c fails to compare server identity verification policies. By ignoring CURLOPTSSHKNOWNHOSTS, CURLOPTSSHHOSTPUBLICKEYMD5...

curl: Use-After-Free race condition in url_move_hostname() via shared connection pool

Summary: In lib/url.c, urlconnreuseadjust calls urlmovehostname which frees conn-host.rawalloc and conn-host.encalloc via Curlsafefree and Curlfreeidnconvertedhostname after Curlcpoolfind has already released the connection pool lock. A second thread doing a concurrent pool lookup still holds tha...

curl: HackerOne Vulnerability Report: libcurl SSL/TLS Identity Leakage via Insecure Connection Reuse

Summary libcurl contains a critical logic flaw in its connection reuse mechanism where transfers using the CURLOPTSSLCTXFUNCTION SSL context callback to establish a specific identity e.g., via client certificates can have their connections incorrectly reused by subsequent, unauthenticated transfe...

curl: Unbounded GZIP Decompression Leading to Event-Loop Starvation

When libcurl is configured to decompress HTTP responses via CURLOPTACCEPTENCODING or the --compressed CLI flag, it lacks decompression bounds checking or a mechanism to yield execution during massive expansion tasks. If an attacker provides a highly compressed payload zip bomb, libcurl's underlyi...

The vulnerability of the libcurl library in software applications for interacting with servers via cURL allows attackers to compromise the confidentiality of protected information.

The vulnerability of the libcurl library in software applications for interacting with servers via cURL is related to improper verification of certificate authenticity. Exploiting this vulnerability allows an attacker to compromise the confidentiality of the protected information...

Curl 7.10.6 < 8.19.0 Authentication Bypass

The version of curl installed on the remote host is 7.10.6 prior to 8.19.0. It is, therefore, affected by an authentication bypass vulnerability: - libcurl can in some circumstances reuse the wrong connection when asked to do an Negotiate-authenticated HTTP or HTTPS request. libcurl features a po...

CVE-2026-1965

libcurl can in some circumstances reuse the wrong connection when asked to do an Negotiate-authenticated HTTP or HTTPS request. libcurl features a pool of recent connections so that subsequent requests can reuse an existing connection to avoid overhead. When reusing a connection a range of...

UBUNTU-CVE-2026-1965

libcurl can in some circumstances reuse the wrong connection when asked to do an Negotiate-authenticated HTTP or HTTPS request. libcurl features a pool of recent connections so that subsequent requests can reuse an existing connection to avoid overhead. When reusing a connection a range of...

SUSE CVE-2026-1965

libcurl can in some circumstances reuse the wrong connection when asked to do an Negotiate-authenticated HTTP or HTTPS request. libcurl features a pool of recent connections so that subsequent requests can reuse an existing connection to avoid overhead. When reusing a connection a range of...

EUVD-2026-11135

libcurl can in some circumstances reuse the wrong connection when asked to do an Negotiate-authenticated HTTP or HTTPS request. libcurl features a pool of recent connections so that subsequent requests can reuse an existing connection to avoid overhead. When reusing a connection a range of...

AZL-79676 CVE-2026-1965 affecting package curl for versions less than 8.11.1-6

libcurl can in some circumstances reuse the wrong connection when asked to do an Negotiate-authenticated HTTP or HTTPS request. libcurl features a pool of recent connections so that subsequent requests can reuse an existing connection to avoid overhead. When reusing a connection a range of...

CVE-2026-1965 bad reuse of HTTP Negotiate connection

libcurl can in some circumstances reuse the wrong connection when asked to do an Negotiate-authenticated HTTP or HTTPS request. libcurl features a pool of recent connections so that subsequent requests can reuse an existing connection to avoid overhead. When reusing a connection a range of...

CVE-2026-1965 bad reuse of HTTP Negotiate connection

libcurl can in some circumstances reuse the wrong connection when asked to do an Negotiate-authenticated HTTP or HTTPS request. libcurl features a pool of recent connections so that subsequent requests can reuse an existing connection to avoid overhead. When reusing a connection a range of...

CVE-2026-1965

libcurl can in some circumstances reuse the wrong connection when asked to do an Negotiate-authenticated HTTP or HTTPS request. libcurl features a pool of recent connections so that subsequent requests can reuse an existing connection to avoid overhead. When reusing a connection a range of...

CVE-2026-1965 bad reuse of HTTP Negotiate connection

libcurl can in some circumstances reuse the wrong connection when asked to do an Negotiate-authenticated HTTP or HTTPS request. libcurl features a pool of recent connections so that subsequent requests can reuse an existing connection to avoid overhead. When reusing a connection a range of...

CVE-2026-1965

libcurl can in some circumstances reuse the wrong connection when asked to do an Negotiate-authenticated HTTP or HTTPS request. libcurl features a pool of recent connections so that subsequent requests can reuse an existing connection to avoid overhead. When reusing a connection a range of...

CVE-2026-1965

libcurl can in some circumstances reuse the wrong connection when asked to do an Negotiate-authenticated HTTP or HTTPS request. libcurl features a pool of recent connections so that subsequent requests can reuse an existing connection to avoid overhead. When reusing a connection a range of...