An HTTP proxy can trick libcurl into sending the origin's credentials (Basic password, or a Negotiate/Kerberos ticket) to the proxy itself, by answering the `CONNECT` tunnel request with 401 `WWW-Authenticate:` instead of the expected 407 `Proxy-Authenticate:`.

An HTTP proxy can trick libcurl into sending the origin's credentials (Basic password, or a Negotiate/Kerberos ticket) to the proxy itself, by answering the `CONNECT` tunnel request with 401 `WWW-Authenticate:` instead of the expected 407 `Proxy-Authenticate:`.

curl-8.23.0-1.1 on GA media

curl: libcurl: Curl out of bounds read for cookie path curl: curl: Security bypass due to global TLS option changes in multi-threaded LDAPS transfers curl: libcurl: Improper certificate validation due to cached TLS settings reuse curl: curl: stale SigV4 headers sent unintended curl: curl: redirect to SFTP or SCP bypasses host verification curl: curl: FTP connection reuse inherits client-certificate curl: curl: server-set cookie erases cookie jar curl: curl: Negotiate credentials sent to redirected origin curl: curl: leaking host credentials to HTTP proxy curl: curl: cross-origin reuse of a Negotiate connection curl: curl: HSTS cache import drops longer-lived child curl: curl: Hsts Response Erases Persisted Entries curl: IMAP APPEND plus CRLF conversion command injection curl: curl: knownhost callback mismatches key as missing curl: curl: wolfSSL public-key pinning bypass curl: curl: server-set cookie aborts cookie jar load curl: curl: never-ending loop via server response omission curl: curl: FTP wildcard write callback mixup curl: curl: TFTP direction confusion curl: curl: -J no-clobber guarantee bypassed with 103 early hints curl: curl: curl_mime_free stack overflow by recursion curl: curl: HTTP/2 upload Use-After-Free curl: curl: Authorization: Negotiate sent to foreign origin curl: curl: password leak in CURLINFO_EFFECTIVE_URL curl: curl: info leak uploading over WebSockets with GnuTLS curl: curl: local interface connection reuse mixup

Affected: Ubuntu:Pro:14.04:LTS: curl, Ubuntu:Pro:16.04:LTS: curl, Ubuntu:Pro:18.04:LTS: curl, Ubuntu:Pro:20.04:LTS: curl, Ubuntu:22.04:LTS: curl, Ubuntu:24.04:LTS: curl, Ubuntu:26.10: curl, Ubuntu:26.04:LTS: curl

A HTTP proxy can trick libcurl into sending the origin's credentials (Basic password, or a Negotiate/Kerberos ticket) to the proxy itself, by answering the `CONNECT` tunnel request with 401 `WWW-Authenticate:` instead of the expected 407 `Proxy-Authenticate:`.