Summary
Mechanize sends credential headers to another host after an HTTP redirect
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.
Details
Two defects, both in lib/mechanize/http/agent.rb.
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.
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.
Cookies 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.
PoC
agent = Mechanize.new
agent.request_headers = { 'Authorization' => 'Bearer secret' }
agent.get('https://example.test/redirects-to-attacker')
# the request to the attacker's host carries "Authorization: Bearer secret"
What this fix does not cover
Only 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.
Workarounds
Set 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.
Credit
Reported by @SnailSploit.
Impact
An 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.
CVE-2026-107715 has a CVSS score of 6.8 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.14.1); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Fixed in mechanize v2.14.1.
- Credentials and cookies are withheld from a request that follows a redirect across an origin, from both header sources: the per-request
headersargument andMechanize#request_headers=. CREDENTIAL_HEADERSgainsProxy-Authorization;COOKIE_HEADERSgainsCookie2.
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.
Headers 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.
Frequently Asked Questions
- What is CVE-2026-107715? CVE-2026-107715 is a medium-severity security vulnerability in mechanize (rubygems), affecting versions < 2.14.1. It is fixed in 2.14.1.
- How severe is CVE-2026-107715? CVE-2026-107715 has a CVSS score of 6.8 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of mechanize are affected by CVE-2026-107715? mechanize (rubygems) versions < 2.14.1 is affected.
- Is there a fix for CVE-2026-107715? Yes. CVE-2026-107715 is fixed in 2.14.1. Upgrade to this version or later.
- Is CVE-2026-107715 exploitable, and should I be worried? Whether CVE-2026-107715 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-107715 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-107715? Upgrade
mechanizeto 2.14.1 or later.