CVE-2026-48595: Tesla Authorization Header Leaks On Cross-origin Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-9m9w-gxf7-rh8m",
  "modified" : "2026-07-10T00:03:31Z",
  "published" : "2026-07-10T00:03:31Z",
  "aliases" : [ "CVE-2026-48595" ],
  "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 <token>\"}`).\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",
  "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"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Hex",
      "name" : "tesla"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0.6.0"
      }, {
        "fixed" : "1.18.3"
      } ]
    } ]
  } ],
  "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"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-178" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-07-10T00:03:31Z",
    "nvd_published_at" : "2026-06-02T20:16:38Z"
  }
}