libcurl vulnerabilities

libcurl has an issue with reusing previously created connections even when TLS or SSH-related options have been changed that should prohibit reuse. Several TLS and SSH settings were left out from the configuration match checks, making them match too easily.

libcurl provides the `CURLOPT_CERTINFO` option to allow applications to request details about a server's certificate chain. Due to an erroneous function, a malicious server could make libcurl built with NSS get stuck in a never-ending busy-loop when trying to retrieve that information.

libcurl-using applications can request a specific client certificate to be used in a transfer. When built with the macOS native TLS library Secure Transport, a malicious user can trick the application into using a file-based certificate instead of the intended one, leading to the wrong client certificate being sent in the TLS handshake.

libcurl may read outside of a heap allocated buffer when doing FTP. A flaw in the string parser for the directory name may lead to a missing NUL byte at the end of the buffer, resulting in the potential to read data beyond the allocated memory area.

Use-after-free vulnerability in libcurl before version 7.50.1 allows attackers to control which connection is used or possibly have unspecified other impact via unknown vectors.

The ConnectionExists function in lib/url.c in libcurl before version 7.47.0 does not properly re-use NTLM-authenticated proxy connections, which might allow remote attackers to authenticate as other users via a request.

libcurl accidentally skips certificate verification for QUIC connections when connecting to a host specified as an IP address in the URL. Therefore, it does not detect impostors or man-in-the-middle attacks.

Due to a mistake in libcurl's WebSocket code, a malicious server can send a particularly crafted packet which makes libcurl get trapped in an endless busy-loop. There is no other way for the application to escape or exit this loop other than killing the thread/process. This might be used to DoS.

The curl_url_get() function in libcurl offers punycode conversions to and from IDN. When converting a name that is exactly 256 bytes, libcurl reads outside a stack-based buffer when built with the macidn IDN backend.

libcurl supports pinning of the server certificate public key for HTTPS transfers. Due to an omission, this check is not performed when connecting with QUIC for HTTP/3, when the TLS backend is wolfSSL. Documentation says the option works with wolfSSL, but fails to specify that it does not for QUIC.

libcurl's ASN1 parser has this utf8asn1str() function used for parsing an ASN.1 UTF-8 string. It can detect an invalid field and return error. Unfortunately, when doing so it also invokes `free()` on a 4 byte local stack buffer. Most modern malloc implementations detect this error and immediately abort.

A vulnerability in the libcurl library causes a memory leak when handling HTTP/2 server push. When an application allows server push and the number of headers exceeds the limit of 1000, libcurl aborts the push but fails to free previously allocated headers.

A flaw in libcurl caused the command to clear proxy authentication credentials to be ineffective, leaving old credentials in memory. These credentials were then used in subsequent transfers that should not have access to them.

A vulnerability in the libcurl library causes a leak of the proxy authorization header between requests. When reusing a libcurl handle for sequential transfers with environment-variable proxy configuration, the proxy authentication state is not cleared between requests. As a result, the `Proxy-Authorization:` header intended for one proxy may be sent to another.

A vulnerability in libcurl causes the Authorization header intended for the original host to be incorrectly forwarded to a different host when reusing a handle for HTTP transfers with Digest authentication.

A vulnerability in the libcurl library involves the connection pool, which may retain connections using default native CA trust. When an application switches a handle to custom CA material, old connections might still be reused with the original trust settings.

A use-after-free vulnerability exists in libcurl when an application configures an HTTP/2 stream-dependency tree via CURLOPT_STREAM_DEPENDS or CURLOPT_STREAM_DEPENDS_E, subsequently invokes curl_easy_reset(), and finally terminates the handle with curl_easy_cleanup(). During this final cleanup phase, libcurl attempts to access and modify an internal structure that was already freed during the reset operation.

A vulnerability in libcurl related to improper handling of IMAP FETCH responses when the data size is zero bytes. The deliver-data function may attempt to read data from a buffer that is not properly terminated, potentially leading to reading memory beyond the allocated area.

Multiple integer overflows in the (1) curl_escape, (2) curl_easy_escape, (3) curl_unescape, and (4) curl_easy_unescape functions in libcurl before version 7.50.3 allow attackers to have unspecified impact via a string of length 0xffffffff, which triggers a heap-based buffer overflow.

A vulnerability in libcurl allows accepting an untrusted server during SCP or SFTP transfers when using the CURLOPT_SSH_KEYFUNCTION callback. The server can present a host key type different from the one recorded in the known_hosts file, and the callback mechanism fails to enforce rejection, allowing the connection to succeed without warning.

A vulnerability in libcurl causes the HTTP `Referer:` header to persist even when explicitly cleared. According to the documentation, passing NULL to `CURLOPT_REFERER` should suppress the header, but the option fails to clear the internal state. As a result, the previous referrer string is erroneously reused and sent in subsequent requests, potentially leaking sensitive information to unintended servers.

A vulnerability in libcurl allows sending the second request's data before enforcing certificate verification when SSL session caching and early data are enabled. This occurs when the target server is replaced by an attacker's impostor machine.

Calling `curl_easy_pause()` within the event-based `CURLMOPT_SOCKETFUNCTION` callback triggers a use-after-free vulnerability. libcurl attempts to store a flag using a dangling struct pointer immediately after that pointer's memory has been freed.

libcurl would reuse a previously created connection even when some mTLS config related option had been changed that should have prohibited reuse. Specifically, options related to the private key were left out from the configuration match checks.

libcurl may in some circumstances reuse the wrong connection when asked to do Negotiate-authenticated ones, even when they are set to use different services. A logical error in the connection pool management causes an application request to incorrectly reuse an existing connection authenticated for a different service.