Axel Download Accelerator Path Traversal via URL Filename Decoding

Axel Download Accelerator 2.17.14 and earlier performs URL percent-decoding (http_decode()) 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.

Source published

28 Oct 2026 11:26:59 UTC

Source modified

28 Oct 2026 11:26:59 UTC

Observed here

28 Oct 2026 12:47:04 UTC

Source terms

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CVSS 4.0 · 7.0 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N

CVSS 3.1 · 8.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H