curl supports the -t
command line option, known as CURLOPT_TELNETOPTIONS
in libcurl. This rarely used option is used to send variable=content pairs to
TELNET servers.
Due to 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. Therefore potentially revealing sensitive internal information to the
server using a clear-text network protocol.
This could happen because curl did not call and use sscanf()
correctly when
parsing the string provided by the application.
The previous curl security vulnerability CVE-2021-22898 is almost identical to this one but the fix was insufficient so this security vulnerability remained.