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 CURLOPTSSLCIPHERLIST 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.