{"id":"CVE-2026-107715","aliases":["GHSA-2mwr-xjcg-37j7"],"url":"https://o3.security/vulnerability/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.","published":"2026-10-08T21:27:24.651Z","modified":"2026-10-21T02:54:37.176715347Z","cvss":{"score":6.8,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:N/A:N"},"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"RubyGems","name":"mechanize","fixedVersion":"2.14.1"}],"fix":{"url":"https://github.com/sparklemotion/mechanize/commit/02a1235842d6eda8d4a5a3d8f13aba2cecf52e4f","label":"sparklemotion/mechanize@02a1235"},"references":[{"type":"WEB","url":"https://github.com/sparklemotion/mechanize/releases/tag/v2.14.1"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/107xxx/CVE-2026-107715.json"},{"type":"ADVISORY","url":"https://github.com/sparklemotion/mechanize/security/advisories/GHSA-2mwr-xjcg-37j7"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-107715"},{"type":"FIX","url":"https://github.com/sparklemotion/mechanize/commit/02a1235842d6eda8d4a5a3d8f13aba2cecf52e4f"},{"type":"FIX","url":"https://github.com/sparklemotion/mechanize/commit/94e0902867296be804f36eccbb47acf7d5018745"},{"type":"FIX","url":"https://github.com/sparklemotion/mechanize/commit/ac49abf2869297d83c3b11bbfb8b18e63b588c95"},{"type":"FIX","url":"https://github.com/sparklemotion/mechanize/pull/676"},{"type":"PACKAGE","url":"https://github.com/sparklemotion/mechanize"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-10-21T02:54:37.176715347Z"}}