The GnuTLS backend in libcurl 7.21.4 through 7.33.0, when disabling digital signature verification (CURLOPT_SSL_VERIFYPEER), also disables the CURLOPT_SSL_VERIFYHOST check for CN or SAN host name fields, which makes it easier for remote attackers to spoof servers and conduct man-in-the-middle (MITM) attacks.

cURL and libcurl 7.18.0 through 7.32.0, when built with OpenSSL, disables the certificate CN and SAN name field verification (CURLOPT_SSL_VERIFYHOST) when the digital signature verification (CURLOPT_SSL_VERIFYPEER) is disabled, which allows man-in-the-middle attackers to spoof SSL servers via an arbitrary valid certificate.

Heap-based buffer overflow in the curl_easy_unescape function in lib/escape.c in cURL and libcurl 7.7 through 7.30.0 allows remote attackers to cause a denial of service (application crash) or possibly execute arbitrary code via a crafted string ending in a "%" (percent) character.

The tailMatch function in cookie.c in cURL and libcurl before 7.30.0 does not properly match the path domain when sending cookies, which allows remote attackers to steal cookies via a matching suffix in the domain of a URL.

Stack-based buffer overflow in the Curl_sasl_create_digest_md5_message function in lib/curl_sasl.c in curl and libcurl 7.26.0 through 7.28.1, when negotiating SASL DIGEST-MD5 authentication, allows remote attackers to cause a denial of service (crash) and possibly execute arbitrary code via a long string in the realm parameter in a (1) POP3, (2) SMTP or (3) IMAP message.

The SSL protocol, as used in certain configurations in Microsoft Windows and Microsoft Internet Explorer, Mozilla Firefox, Google Chrome, Opera, and other products, encrypts data by using CBC mode with chained initialization vectors, which allows man-in-the-middle attackers to obtain plaintext HTTP headers via a blockwise chosen-boundary attack (BCBA) on an HTTPS session, in conjunction with JavaScript code that uses (1) the HTML5 WebSocket API, (2) the Java URLConnection API, or (3) the Silverlight WebClient API, aka a "BEAST" attack.

The Curl_input_negotiate function in http_negotiate.c in libcurl 7.10.6 through 7.21.6, as used in curl and other products, always performs credential delegation during GSSAPI authentication, which allows remote servers to impersonate clients via GSSAPI requests.

Multiple stack-based buffer overflows in libcURL and cURL 7.12.1, and possibly other versions, allow remote malicious web servers to execute arbitrary code via base64 encoded replies that exceed the intended buffer lengths when decoded, which is not properly handled by (1) the Curl_input_ntlm function in http_ntlm.c during NTLM authentication or (2) the Curl_krb_kauth and krb4_auth functions in krb4.c during Kerberos authentication.