CVE-2026-107399 — Vulnerability in mechanize — CVE Details

## Summary `mechanize` applied no trust boundary to a `meta` refresh, so credentials set through `Mechanize#request_headers=` followed a refresh that pointed at another origin. ## Details `Mechanize::HTTP::Agent#response_follow_meta_refresh` fetched the refresh target with no notion of a crossed origin, so `@request_headers` were re-applied in full. An attacker who could place a `meta` refresh in a page the agent fetched — through stored content, an open redirect, or control of any page in the crawl — collected the same credentials as through an HTTP redirect, on a code path that had none of the redirect path's protections. The refresh fetch passes an empty per-request headers hash, so only headers set through `Mechanize#request_headers=` were exposed. This requires `Mechanize#follow_meta_refresh = true`. It is `false` by default, so an agent in its default configuration is not affected. Crawlers commonly enable it. ## Impact An attacker who can place a `meta` refresh in any page the agent fetches captures bearer tokens and session cookies set through `request_headers=`. Disclosure only; no integrity or availability impact. ## Patches Fixed in `mechanize` v2.14.1. A `meta` refresh that points at another origin is now subject to the same rule as an HTTP redirect: credentials and cookies are withheld from the request that follows it. ## Workarounds Leave `Mechanize#follow_meta_refresh` at its default of `false`, or avoid `request_headers=` for credentials when it is enabled.