CVE-2026-54605: OAuth Cross-origin Token-request Redirects Can Expose Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-prq8-7wvh-44qh",
  "modified" : "2026-07-28T16:27:11Z",
  "published" : "2026-07-28T16:27:11Z",
  "aliases" : [ "CVE-2026-54605" ],
  "summary" : "OAuth: Cross-origin token-request redirects can expose signed request metadata",
  "details" : "# Cross-origin OAuth token-request redirects can expose signed request metadata\n\n## Summary\n\nWhen an application uses `OAuth::Consumer` to request OAuth 1.0 request tokens or\naccess tokens, the token request helper follows `300..399` redirects returned by\nthe OAuth server. In affected versions, `OAuth::Consumer#token_request` parses the\nraw `Location` header, follows the redirect recursively, and can mutate the\nconsumer's configured `site` when the redirect points to a different host with\nthe same path.\n\nThe result is a cross-origin signed-request disclosure primitive: if an OAuth\nserver token endpoint returns a redirect whose target an attacker controls, the\nclient can re-sign the token request and send OAuth 1.0 request metadata,\nincluding the OAuth signature, nonce, timestamp, consumer key, and any request\nparameters included in the signature base string, to the attacker-controlled\nhost. The same behavior can also be used as an SSRF or confused-deputy primitive\nbecause the application server follows the redirect and sends the next request\nfrom its own network position.\n\n## Affected\n\n- `oauth` v1.1.5 and prior versions back to and including v0.5.5.\n  - The cross-host token redirect behavior was introduced by\n    https://github.com/ruby-oauth/oauth/commit/d74b767f\n  - The behavior is documented in the v0.5.5 changelog as \"Allow redirect to\n    different host but same path\".\n- The vulnerable behavior is in `OAuth::Consumer#token_request`, which is used by\n  the documented request-token and access-token flows.\n- The issue is not specific to a Ruby engine or platform. It is caused by the\n  gem's redirect handling and recursive token request behavior.\n\nPatched version: `oauth` v1.1.6.\n\n## Impact\n\nA consumer that calls `OAuth::Consumer#get_request_token`,\n`OAuth::Consumer#get_access_token`, or lower-level token request helpers against\nan OAuth server whose token endpoint redirect target can be influenced may lose\nthree security properties:\n\n1. **Cross-origin signed-request metadata disclosure.** The redirected request is\n   signed for the attacker-controlled endpoint. Depending on the request method,\n   scheme, and parameters, the attacker may receive OAuth 1.0 parameters such as\n   `oauth_consumer_key`, `oauth_signature_method`, `oauth_timestamp`,\n   `oauth_nonce`, `oauth_version`, and `oauth_signature`.\n2. **SSRF from the application server.** The OAuth client follows the redirect on\n   behalf of the application, so the redirected host is contacted from the\n   application server's network position.\n3. **Confused-deputy behavior.** A malicious or compromised token endpoint can\n   cause an otherwise trusted application to initiate signed requests to an\n   unintended origin.\n\nThe disclosed OAuth 1 signature is not equivalent to an OAuth 2 bearer token: it\nis bound to the signed request, timestamp, nonce, HTTP method, and request URL.\nHowever, it can still disclose sensitive integration metadata, may be replayable\nwithin the receiver's accepted nonce/timestamp window in some deployments, and\ncan expose application-server reachability to attacker-selected hosts.\n\n## Vulnerable code\n\n[`lib/oauth/consumer.rb`](https://github.com/ruby-oauth/oauth/blob/v1.1.5/lib/oauth/consumer.rb)\nat tag `v1.1.5`:\n\n```ruby\ndef token_request(http_method, path, token = nil, request_options = {}, *arguments)\n  request_options[:token_request] ||= true\n  response = request(http_method, path, token, request_options, *arguments)\n  case response.code.to_i\n\n  when (200..299)\n    # parse token response\n  when (300..399)\n    # Parse redirect to follow\n    uri = URI.parse(response[\"location\"])\n    our_uri = URI.parse(site)\n\n    # Guard against infinite redirects\n    response.error! if uri.path == path && our_uri.host == uri.host\n\n    if uri.path == path && our_uri.host != uri.host\n      options[:site] = \"#{uri.scheme}://#{uri.host}\"\n      @http = create_http\n    end\n\n    token_request(http_method, uri.path, token, request_options, arguments)\n  when (400..499)\n    raise OAuth::Unauthorized, response\n  else\n    response.error!\n  end\nend\n```\n\nThe vulnerable behavior has several parts:\n\n- `response[\"location\"]` is trusted as the next token request target.\n- Redirects are followed for every `300..399` response.\n- There is no general redirect counter or maximum redirect limit.\n- Cross-host redirects with the same path can mutate `options[:site]` and rebuild\n  the underlying HTTP client.\n- The recursive call continues the token request flow and signs the next request\n  for the redirected destination.\n\n## Reachable in production\n\nThe vulnerable path is reachable through the normal OAuth 1 token exchange:\n\n```ruby\nconsumer = OAuth::Consumer.new(\n  consumer_key,\n  consumer_secret,\n  site: \"https://provider.example\"\n)\n\nrequest_token = consumer.get_request_token\n```\n\nIf `https://provider.example/oauth/request_token` returns a redirect to an\nattacker-controlled host, the library follows that redirect as part of the token\nrequest flow. A realistic trigger is an OAuth provider, gateway, or reverse proxy\nthat emits `Location` based on user-controlled or tenant-controlled input, or a\nmalicious tenant-controlled OAuth endpoint in a multi-tenant integration.\n\nNo application-level redirect handling is required. The redirect is followed\ninside the gem before the application receives the token response.\n\n## Reproduction\n\nA vulnerable application is one that uses `OAuth::Consumer` to perform an OAuth\n1 token exchange against a token endpoint that can be made to return a redirect\nto another origin.\n\nExample shape:\n\n```ruby\nconsumer = OAuth::Consumer.new(\n  consumer_key,\n  consumer_secret,\n  site: \"https://provider.example\"\n)\n\nconsumer.get_request_token\n```\n\nIf `https://provider.example/oauth/request_token` responds with a `30x` redirect\nwhose `Location` points to `https://attacker.example/...`, affected versions may\nfollow that redirect as part of the token request flow. The redirected request is\nthen generated and signed by the application server for the new destination.\nDepending on the configured OAuth request scheme, OAuth 1 parameters may be sent\nin the `Authorization` header, request body, or query string.\n\nExpected vulnerable behavior:\n\n- the token request leaves the configured OAuth provider origin;\n- the redirected host receives a signed OAuth 1 token request;\n- the application does not get a chance to inspect or approve the redirect target\n  before the redirected request is sent.\n\nExpected patched behavior:\n\n- same-origin redirects continue to work, subject to a redirect limit;\n- cross-origin token endpoint redirects are rejected by default;\n- applications that intentionally require cross-origin token redirects must opt\n  in explicitly with `token_request_cross_origin_redirects`.\n\n## Suggested fix\n\nReject cross-origin token endpoint redirects by default and require explicit\nopt-in for integrations that intentionally depend on that behavior.\n\nThe fix released in v1.1.6 does the following:\n\n```ruby\ncurrent_uri = token_request_uri(path)\nredirected_uri = token_request_redirect_uri(current_uri, response)\nresponse.error! unless redirected_uri\n\nredirect_count = request_options[:token_request_redirect_count].to_i + 1\nresponse.error! if redirect_count > token_request_max_redirects(request_options)\nresponse.error! if token_request_cross_origin?(current_uri, redirected_uri) &&\n  !token_request_cross_origin_redirects?(request_options)\n\nredirect_options = request_options.merge(token_request_redirect_count: redirect_count)\ntoken_request(http_method, token_request_redirect_path(current_uri, redirected_uri), token, redirect_options, *arguments, &block)\n```\n\nThe fix intentionally preserves same-origin redirect compatibility while making\ncross-origin token endpoint redirects an explicit choice. It also avoids placing\ninternal redirect state in `request_options` passed to OAuth signing.\n\n## Workarounds\n\nUntil a patched release is available, applications can reduce exposure by doing\none or more of the following:\n\n- Ensure configured OAuth token endpoints are fixed absolute URLs controlled by a\n  trusted provider.\n- Do not use tenant-controlled OAuth token endpoint URLs unless the tenant is\n  trusted to receive signed OAuth token requests.\n- Block outbound application-server traffic to internal metadata services and\n  other sensitive internal addresses at the network layer.\n- Place a trusted proxy in front of OAuth providers that rejects token endpoint\n  redirects to a different origin.\n\nThese mitigations reduce exploitability but do not remove the vulnerable redirect\nlogic from the gem.\n\n## Credit\n\nFound during the follow-up audit for `GHSA-pp92-crg2-gfv9`.\n\nReporter/coordinator: Peter H. Boling (`pboling`).\n\n## References\n\n- Related OAuth 2 advisory: https://github.com/ruby-oauth/oauth2/security/advisories/GHSA-pp92-crg2-gfv9\n- Fixed version: `oauth` v1.1.6\n- Behavior-introducing commit: https://github.com/ruby-oauth/oauth/commit/d74b767f",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "RubyGems",
      "name" : "oauth"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0.5.5"
      }, {
        "fixed" : "1.1.6"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 1.1.5"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/ruby-oauth/oauth/security/advisories/GHSA-prq8-7wvh-44qh"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/ruby-oauth/oauth/commit/d069dc8c4c9631947451215f07460d6cdf0caf3f"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/ruby-oauth/oauth"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/ruby-oauth/oauth/releases/tag/v1.1.6"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-200", "CWE-346", "CWE-918" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-07-28T16:27:11Z",
    "nvd_published_at" : null
  }
}