Open Source Curl Remote Code Execution Vulnerability

A user can tell curl >= 7.20.0 and <= 7.78.0 to require a successful upgrade to TLS when speaking to an IMAP POP3 or FTP server (`--ssl-reqd` on the command line or`CURLOPT_USE_SSL` set to `CURLUSESSL_CONTROL` or `CURLUSESSL_ALL` withlibcurl). This requirement could be bypassed if the server would return a properly crafted but perfectly legitimate response.This flaw would then make curl silently continue its operations **withoutTLS** contrary to the instructions and expectations exposing possibly sensitive data in clear text over the network.

When sending data to an MQTT server libcurl <= 7.73.0 and 7.78.0 could in some circumstances erroneously keep a pointer to an already freed memory area and both use that again in a subsequent call to send data and also free it *again*.

Node.js before 16.6.1 14.17.5 and 12.22.5 is vulnerable to a use after free attack where an attacker might be able to exploit the memory corruption to change process behavior.

If the Node.js https API was used incorrectly and "undefined" was in passed for the "rejectUnauthorized" parameter no error was returned and connections to servers with an expired certificate would have been accepted.

Node.js before 16.6.0 14.17.4 and 12.22.4 is vulnerable to a use after free attack where an attacker might be able to exploit the memory corruption to change process behavior.

libcurl-using applications can ask for a specific client certificate to be used in a transfer. This is done with the `CURLOPT_SSLCERT` option (`--cert` with the command line tool).When libcurl is built to use the macOS native TLS library Secure Transport an application can ask for the client certificate by name or with a file name - using the same option. If the name exists as a file it will be used instead of by name.If the appliction runs with a current working directory that is writable by other users (like `/tmp`) a malicious user can create a file name with the same name as the app wants to use by name and thereby trick the application to use the file based cert instead of the one referred to by name making libcurl send the wrong client certificate in the TLS connection handshake.

curl supports the `-t` command line option known as `CURLOPT_TELNETOPTIONS`in libcurl. This rarely used option is used to send variable=content pairs toTELNET servers.Due to flaw in the option parser for sending `NEW_ENV` variables libcurlcould be made to pass on uninitialized data from a stack based buffer to theserver. Therefore potentially revealing sensitive internal information to theserver using a clear-text network protocol.This could happen because curl did not call and use sscanf() correctly whenparsing the string provided by the application.

libcurl keeps previously used connections in a connection pool for subsequenttransfers to reuse if one of them matches the setup.Due to errors in the logic the config matching function did not take 'issuercert' into account and it compared the involved paths *case insensitively*which could lead to libcurl reusing wrong connections.File paths are or can be case sensitive on many systems but not all and caneven vary depending on used file systems.The comparison also didn't include the 'issuer cert' which a transfer can setto qualify how to verify the server certificate.

When curl is instructed to get content using the metalink feature and a user name and password are used to download the metalink XML file those same credentials are then subsequently passed on to each of the servers from which curl will download or try to download the contents from. Often contrary to the user's expectations and intentions and without telling the user it happened.

When curl is instructed to download content using the metalink feature thecontents is verified against a hash provided in the metalink XML file.The metalink XML file points out to the client how to get the same contentfrom a set of different URLs potentially hosted by different servers and theclient can then download the file from one or several of them. In a serial orparallel manner.If one of the servers hosting the contents has been breached and the contentsof the specific file on that server is replaced with a modified payload curlshould detect this when the hash of the file mismatches after a completeddownload. It should remove the contents and instead try getting the contentsfrom another URL. This is not done and instead such a hash mismatch is onlymentioned in text and the potentially malicious content is kept in the file ondisk.

curl 7.75.0 through 7.76.1 suffers from a use-after-free vulnerability resulting in already freed memory being used when a TLS 1.3 session ticket arrives over a connection. A malicious server can use this in rare unfortunate circumstances to potentially reach remote code execution in the client. When libcurl at run-time sets up support for TLS 1.3 session tickets on a connection using OpenSSL it stores pointers to the transfer in-memory object for later retrieval when a session ticket arrives. If the connection is used by multiple transfers (like with a reused HTTP/1.1 connection or multiplexed HTTP/2 connection) that first transfer object might be freed before the new session is established on that connection and then the function will access a memory buffer that might be freed. When using that memory libcurl might even call a function pointer in the object making it possible for a remote code execution if the server could somehow manage to get crafted memory content into the correct

curl 7.7 through 7.76.1 suffers from an information disclosure when the `-t` command line option known as `CURLOPT_TELNETOPTIONS` in libcurl is used to send variable=content pairs to TELNET servers. Due to a flaw in the option parser for sending NEW_ENV variables libcurl could be made to pass on uninitialized data from a stack based buffer to the server resulting in potentially revealing sensitive internal information to the server using a clear-text network protocol.

curl 7.61.0 through 7.76.1 suffers from exposure of data element to wrong session due to a mistake in the code for CURLOPT_SSL_CIPHER_LIST when libcurl is built to use the Schannel TLS library. The selected cipher set was stored in a single "static" variable in the library which has the surprising side-effect that if an application sets up multiple concurrent transfers the last one that sets the ciphers will accidentally control the set used by all transfers. In a worst-case scenario this weakens transport security significantly.