CVE-2026-107714 in Mechanize
Summary
by MITRE • 10/09/2026
The Mechanize library is used for automating interaction with websites. Prior to 2.14.1, Mechanize::HTTP::Agent#response_redirect treats redirects as same-origin when the host matches without consistently comparing scheme and port. A same-host HTTPS-to-HTTP redirect can send Authorization and Cookie headers over cleartext, while a same-host redirect to another port can send a caller-supplied Cookie header to a different service. Cookies in Mechanize#cookie_jar remain scoped separately; the issue affects caller-supplied headers and can disclose credentials without affecting integrity or availability. This issue is fixed in version 2.14.1.
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Analysis
by VulDB Data Team • 10/09/2026
The Mechanize library serves as a critical tool for automating interactions with web services, allowing developers to programmatically navigate websites and handle form submissions. A significant security flaw was identified within the HTTP agent component of this library, specifically affecting how redirect responses are processed prior to version 2.14.1. The vulnerability stems from an inconsistent implementation in the response_redirect method, which incorrectly treats redirects as same-origin when only the host name matches. This logic fails to adequately verify that the scheme and port remain identical between the original request and the redirected target. Consequently, the library does not strictly enforce origin boundaries based on all three components of a URL: scheme, host, and port.
This technical flaw leads to severe information disclosure risks when an application relies on Mechanize for automated browsing or API interactions. In scenarios where a server issues a redirect from HTTPS to HTTP while maintaining the same hostname, the library continues to attach sensitive headers such as Authorization tokens and cookies to the subsequent request. Because the connection switches to cleartext HTTP during this transition, these credentials are transmitted unencrypted over the network. This exposes authentication details to potential interception by malicious actors performing man-in-the-middle attacks or monitoring local network traffic. The vulnerability effectively undermines the security guarantees provided by HTTPS, as the confidentiality of sensitive data is compromised despite the initial request being secure.
Furthermore, the issue extends beyond protocol downgrades to include port-based redirections. If a redirect occurs from one port to another on the same host, Mechanize may forward caller-supplied Cookie headers to the new destination service. This behavior can result in credential leakage across different services or applications hosted on the same server but operating on distinct ports. Since cookies are scoped separately within the library's cookie jar for standard operations, this specific flaw affects only explicitly supplied headers rather than automatically managed session data. The impact is primarily limited to confidentiality and integrity of credentials; availability remains unaffected as the requests still proceed successfully, albeit with exposed sensitive information.
From a classification perspective, this vulnerability aligns closely with CWE-319, which describes cleartext transmission of sensitive information over an insecure channel. It also relates to CWE-200, concerning exposure of sensitive information to unauthorized actors. In terms of the MITRE ATT&CK framework, this behavior facilitates credential access through network sniffing or interception during transit, mapping to techniques associated with Credential Access and potentially Initial Access if intercepted credentials are used for further exploitation. The root cause is a failure in strict origin validation logic within the HTTP client implementation, highlighting the importance of comprehensive URL parsing that accounts for scheme and port alongside host identity when determining same-origin policy applicability.
To mitigate this risk, organizations using Mechanize must upgrade to version 2.14.1 or later immediately. This release corrects the redirect handling logic to ensure that Authorization and Cookie headers are not sent unless the destination URL matches the origin in scheme, host, and port. Developers should also review their application code for any reliance on automatic header forwarding during redirects and consider implementing additional validation layers if they must handle complex redirection chains. Regularly updating third-party dependencies is essential to maintain a secure posture against such implementation flaws that can inadvertently expose sensitive authentication data.