Vulnerability advisory

EEF-CVE-2026-48595

Authorization header leaks to third-party origin on cross-origin redirect in Tesla.Middleware.FollowRedirects

Published Jun 2, 2026Updated Sep 24, 2026OSV record ↗

Also known as CVE-2026-48595GHSA-9m9w-gxf7-rh8m

Severity

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

Affected versions

tesla Hex

All tesla advisories →

Affected	Fixed in
`1.4.0` to before 1.18.3	`1.18.3`Advisories →
Also listed as affected (40) `1.10.0` `1.10.1` `1.10.2` `1.10.3` `1.11.0` `1.11.1` `1.11.2` `1.12.0` `1.12.1` `1.12.2` `1.12.3` `1.13.0` `1.13.1` `1.13.2` `1.14.0` `1.14.1` `1.14.2` `1.14.3` `1.15.0` `1.15.1` `1.15.2` `1.15.3` `1.16.0` `1.17.0` `1.18.0` `1.18.1` `1.18.2` `1.4.0` `1.4.1` `1.4.2` `1.4.3` `1.4.4` `1.5.0` `1.5.1` `1.6.0` `1.6.1` `1.7.0` `1.8.0` `1.8.1` `1.9.0`

Repository

Affected commits	Fixed by commit
GIT github.com/elixir-tesla/tesla ↗
2d937d5813d7cda5cd726f41824985fb655c920f to before db963dba67651b9abd1fc420a1d9679cf6efe182	`db963dba67651b9abd1fc420a1d9679cf6efe182`

Description

Summary

Improper Handling of Case Sensitivity vulnerability in elixir-tesla tesla allows credential leakage to a third-party origin on cross-origin redirects.

Tesla.Middleware.FollowRedirects strips security-sensitive headers on cross-origin redirects using a case-sensitive string comparison against a lowercase filter list (@filter_headers ["authorization", "host"]). HTTP header names are case-insensitive per RFC 7230, but Tesla preserves header keys verbatim as supplied by the caller without normalizing case. A header set as {"Authorization", "Bearer ..."} (the RFC 7235 canonical casing used by virtually all HTTP libraries and documentation) does not match the lowercase filter entry and is forwarded to the redirect destination. An attacker who can control or influence a Location: response seen by the client (via their own endpoint, a redirect-open upstream, or a compromised origin) receives the bearer token or other Authorization material on the cross-origin request.

This issue affects tesla: from 1.4.0 before 1.18.3.

Workarounds

Normalize all header keys to lowercase before passing them to Tesla. Use "authorization" instead of "Authorization" when setting headers via Tesla.put_header/3 or Tesla.Middleware.Headers.

Configurations

The application must include Tesla.Middleware.FollowRedirects in its Tesla middleware pipeline.