CVE-2026-107715: Mechanize Mechanize Sends Credential Headers To Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-2mwr-xjcg-37j7",
  "modified" : "2026-10-08T22:09:00Z",
  "published" : "2026-10-08T22:09:00Z",
  "aliases" : [ "CVE-2026-107715" ],
  "summary" : "Mechanize sends credential headers to another host after an HTTP redirect",
  "details" : "## Summary\n\n`mechanize` leaked credentials to the redirect target when an HTTP redirect crossed to another host. Credentials set through `Mechanize#request_headers=` leaked even when they were `Authorization`.\n\n## Details\n\nTwo defects, both in `lib/mechanize/http/agent.rb`.\n\n**1. `Mechanize#request_headers=` bypassed the redirect strip entirely.** `#request_add_headers` copied `@request_headers` onto every request unconditionally, with no host check, including the request issued after a redirect. The strip in `#response_redirect` mutated only the per-request headers hash and never touched agent state. Because `request_headers=` is the documented way to set a default credential for every request, the header the code explicitly protected — `Authorization` — was the one most likely to leak.\n\n**2. The strip list omitted `Proxy-Authorization` and `Cookie2`.** Only `CREDENTIAL_HEADERS = ['Authorization']` and `COOKIE_HEADERS = ['Cookie']` were removed from the per-request headers hash on a cross-host redirect.\n\nCookies held in `Mechanize#cookie_jar` and credentials held in `Mechanize::HTTP::AuthStore` are **not** affected. Both are looked up per-URI, so they never follow a redirect to a foreign host. The exposure was limited to headers the caller set by hand.\n\n## PoC\n\n```ruby\nagent = Mechanize.new\nagent.request_headers = { 'Authorization' => 'Bearer secret' }\nagent.get('https://example.test/redirects-to-attacker')\n# the request to the attacker's host carries \"Authorization: Bearer secret\"\n```\n\n## Impact\n\nAn attacker who controls a redirect target — through an open redirect on the site being fetched, an attacker-supplied fetch URL, DNS rebinding, or MITM — captures bearer tokens and session cookies from any `mechanize` agent that sets credentials through `request_headers=` or the per-request `headers` argument. Disclosure only; no integrity or availability impact.\n\n## Patches\n\nFixed in `mechanize` v2.14.1.\n\n- Credentials and cookies are withheld from a request that follows a redirect across an origin, from **both** header sources: the per-request `headers` argument and `Mechanize#request_headers=`.\n- `CREDENTIAL_HEADERS` gains `Proxy-Authorization`; `COOKIE_HEADERS` gains `Cookie2`.\n\n`Proxy-Authorization` is withheld here although curl does not withhold it, because `Net::HTTP` tunnels `https:` requests with `CONNECT`, so a caller-supplied `Proxy-Authorization` travels inside the tunnel to the origin server rather than to the proxy.\n\nHeaders set through `Mechanize#request_headers=` no longer reach a redirect target on another origin when they are credentials. Callers that relied on the previous behavior will see those headers withheld.\n\n### What this fix does not cover\n\nOnly the headers in `CREDENTIAL_HEADERS` and `COOKIE_HEADERS` are withheld. A caller-supplied header that carries a credential under some other name — `X-API-Key`, `X-Vault-Token`, or any bespoke token header — still follows a redirect to another origin, matching the behavior of curl's `CURLOPT_HTTPHEADER`. If you set such a header, do not enable redirect following for requests that carry it, or scope it to a single request whose destination you control.\n\n## Workarounds\n\nSet `Mechanize#redirect_ok = false` and handle redirects explicitly, or avoid `request_headers=` for credentials and pass them per-request only to hosts you intend to authenticate to.\n\n## Credit\n\nReported by @SnailSploit.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:N/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "RubyGems",
      "name" : "mechanize"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "2.14.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/sparklemotion/mechanize/security/advisories/GHSA-2mwr-xjcg-37j7"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/sparklemotion/mechanize/pull/676"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/sparklemotion/mechanize/commit/02a1235842d6eda8d4a5a3d8f13aba2cecf52e4f"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/sparklemotion/mechanize/commit/94e0902867296be804f36eccbb47acf7d5018745"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/sparklemotion/mechanize/commit/ac49abf2869297d83c3b11bbfb8b18e63b588c95"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/sparklemotion/mechanize"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/sparklemotion/mechanize/releases/tag/v2.14.1"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-200", "CWE-522" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-10-08T22:09:00Z",
    "nvd_published_at" : null
  }
}