CRLF injection in Tesla.Multipart disposition parameters allows multipart part header injection

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Improper Encoding or Escaping of Output vulnerability in elixir-tesla tesla allows multipart part header injection via unescaped Content-Disposition parameter values. Tesla.Multipart.part_headers_for_disposition/1 interpolates each disposition parameter as #{k}="#{v}" with no validation of CR (\r), LF (\n), or double-quote characters. The values come verbatim from the caller via Tesla.Multipart.add_field/4 (the name parameter), Tesla.Multipart.add_file/3, and Tesla.Multipart.add_file_content/4 (both the filename parameter and other disposition opts). A " in the value closes the quoted parameter early; a \r\n ends the Content-Disposition header line and starts a new part header (such as a forged Content-Type), or, after a second \r\n, ends the entire part header block and prepends bytes to the part body. The default-filename path in add_file/3 derives the filename via Path.basename/1, which does not strip CR or LF, so any application forwarding a partially-attacker-controlled file path inherits the same issue. This issue affects tesla: from 0.8.0 before 1.18.3.

Source published

2 Jun 2026 19:08:19 UTC

Source modified

24 Sep 2026 21:00:20 UTC

Observed here

23 Oct 2026 15:48:27 UTC

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CVSS 4.0 · 2.1 CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N