Axel Download Accelerator 2.17.14 and earlier performs URL percent-decoding (httpdecode()) on the output filename after the URL has been parsed and the filename component extracted. This allows an attacker to embed %2e%2e%2f (URL-encoded ../) sequences in the URL path. These sequences survive the URL parser intact (they contain no literal / characters) but are decoded into directory traversal sequences before the output file is opened for writing. As a result, a crafted URL can cause axel to write downloaded content to arbitrary filesystem paths relative to the current working directory.

Buffer overflow in the HTTP redirection capability in conn.c for Axel before 1.0b may allow remote attackers to execute arbitrary code.