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

Summary

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.

Timeline

1. Jun 2, 2026, 7:08 PM UTCCVE published
2. Jun 3, 2026, 2:58 PM UTCCISA SSVC assessment

   Exploitation: poc · Automatable: no · Technical impact: partial

3. Sep 24, 2026, 9:00 PM UTCRecord last updated

Affected versions

• tesla

  From 0.8.0 · fixed in 1.18.3

• elixir-tesla/tesla

  From 6ebfdb9abe9c6f119408045b933d82462decd351 · fixed in bb1a2c3da2775924d96e3db8e315dcc4d5d2246e

• teslaHex

  From 0.8.0 · fixed in 1.18.3

References 5