{"id":"GHSA-9m9w-gxf7-rh8m","summary":"Tesla: Authorization header leaks on cross-origin redirect via case-sensitive filtering","details":"### Summary\n\n`Tesla.Middleware.FollowRedirects` is meant to strip the `Authorization` header when following a cross-origin redirect, but performs the check with a case-sensitive comparison against the lowercase string `\"authorization\"`. Because Tesla preserves header keys exactly as supplied by the caller, any application that sets the header with its RFC 7235 canonical casing (`\"Authorization\"`) bypasses the filter entirely, leaking bearer tokens or other credentials to whatever origin the redirect points at.\n\n### Details\n\nThe filter list in `lib/tesla/middleware/follow_redirects.ex` is defined as `@filter_headers [\"authorization\", \"host\"]` and the membership check `k not in @filter_headers` compares the raw key string without case normalization. HTTP header names are case-insensitive per RFC 7230, but Tesla stores them verbatim. A header tuple `{\"Authorization\", \"Bearer …\"}` does not match `\"authorization\"`, so it passes through the filter and is forwarded to the redirect destination unchecked. The same defect applies to the `\"Host\"` entry.\n\nAn attacker who can control a `Location:` response seen by the victim client (their own endpoint, a redirect-open service, or a compromised upstream) receives the credential on the cross-origin follow. No special configuration is required beyond the victim using the standard header casing.\n\n### PoC\n\n1. Configure a Tesla client with `Tesla.Middleware.FollowRedirects` and set the `Authorization` header using canonical casing (`{\"Authorization\", \"Bearer \u003ctoken\u003e\"}`).\n2. Make a request to an endpoint that returns a `302` redirect to a different origin.\n3. Observe that the `Authorization` header with its value is present in the request delivered to the redirect destination.\n\n### Impact\n\nHigh severity (CVSS v4.0: 8.2). Any application using `tesla` 1.4.0 through 1.18.2 with `Tesla.Middleware.FollowRedirects` and a non-lowercase `Authorization` header is affected. The workaround is to use all-lowercase `\"authorization\"` as the header key until upgrading to 1.18.3.\n\n### Workarounds\n\nNormalize 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`.\n\n### Resources\n\n* Introduction commit: https://github.com/elixir-tesla/tesla/commit/2d937d5813d7cda5cd726f41824985fb655c920f\n* Patch commit: https://github.com/elixir-tesla/tesla/commit/db963dba67651b9abd1fc420a1d9679cf6efe182","aliases":["CVE-2026-48595","EEF-CVE-2026-48595"],"modified":"2026-07-10T00:15:09.257114556Z","published":"2026-07-10T00:03:31Z","database_specific":{"severity":"HIGH","github_reviewed":true,"github_reviewed_at":"2026-07-10T00:03:31Z","nvd_published_at":"2026-06-02T20:16:38Z","cwe_ids":["CWE-178"]},"references":[{"type":"WEB","url":"https://github.com/elixir-tesla/tesla/security/advisories/GHSA-9m9w-gxf7-rh8m"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-48595"},{"type":"WEB","url":"https://github.com/elixir-tesla/tesla/commit/db963dba67651b9abd1fc420a1d9679cf6efe182"},{"type":"WEB","url":"https://cna.erlef.org/cves/CVE-2026-48595.html"},{"type":"PACKAGE","url":"https://github.com/elixir-tesla/tesla"},{"type":"WEB","url":"https://osv.dev/vulnerability/EEF-CVE-2026-48595"}],"affected":[{"package":{"name":"tesla","ecosystem":"Hex","purl":"pkg:hex/tesla"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0.6.0"},{"fixed":"1.18.3"}]}],"versions":["0.10.0","0.6.0","0.7.0","0.7.1","0.7.2","0.8.0","0.9.0","1.0.0","1.0.0-beta.1","1.1.0","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","1.2.0","1.2.1","1.3.0","1.3.1","1.3.2","1.3.3","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"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/07/GHSA-9m9w-gxf7-rh8m/GHSA-9m9w-gxf7-rh8m.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N"}]}