curl: [SFTP] TOCTOU Race Condition in Upload Resume Logic Leads to Arbitrary File Append

Summary: A Time-of-check to Time-of-use TOCTOU race condition exists in the SFTP upload resume functionality of libcurl. When resuming an upload with CURLOPTRESUMEFROM set to -1 the equivalent of the curl -C - command-line flag, libcurl first performs a STAT operation to determine the remote file...