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The vulnerability resides within the Ruby Mechanize library, specifically inside the HTTP agent component responsible for handling automated web browsing tasks.
When automated crawlers or scripts enable the meta refresh follow setting via Mechanizefollow_meta_refresh = true, the agent parses HTML content for meta refresh tags.
Upon encountering a meta refresh tag pointing to a new destination, the agent automatically follows the redirect instruction.
Historically, Mechanize failed to implement a proper origin trust boundary during this meta refresh handling process.
Unlike standard HTTP redirects which enforce strict same-origin checks before forwarding sensitive authentication headers, the meta refresh handler lacked these security checks.
As a result, sensitive credential headers previously established through `Mechanizerequest_headers=` were re-applied in full to the new cross-origin request target.
An attacker capable of injecting or hosting a malicious meta refresh tag within any page processed by the crawler could exploit this design flaw.
This injection vector could be achieved through stored user content, open redirect vulnerabilities, or compromised pages encountered during a multi-page crawl.
When the crawler processes the malicious page, it blindly follows the meta refresh instruction while transmitting cached authorization headers.
These headers frequently contain sensitive session tokens, bearer tokens, or authentication credentials configured globally or per-request.
Because the request path passes an empty per-request headers hash, only headers explicitly set via `Mechanizerequest_headers=` are exposed to the external recipient.
By default, `Mechanizefollow_meta_refresh` is set to false, meaning agents using out-of-the-box configurations remain unexposed to this specific risk vector.
However, web scraping bots, automated testing suites, and custom crawlers routinely enable this option to navigate multi-step web workflows seamlessly.
Remediation for this security flaw requires upgrading the Mechanize library to version 2.14.1 or later.
In version 2.14.1, any meta refresh directive pointing to an alternate origin now strictly adheres to standard HTTP redirect security rules.
Consequently, credentials and cookies are withheld from any subsequent cross-origin request triggered via meta refresh.
Alternatively, administrators can mitigate the risk by keeping `follow_meta_refresh` disabled or avoiding global request header credentials when enabled.
DailyCVE Form:
Platform: Mechanize gem
Version: v2.14.1
Vulnerability: Header leak
Severity: Medium severity
date: June 2022
Prediction: Already patched
(end of form)
What Undercode Say
Check current installed mechanize version gem list mechanize Update mechanize to the patched version gem update mechanize Or specify version in Gemfile bundle add mechanize --version "~> 2.14.1"
require 'mechanize' agent = Mechanize.new Safe default configuration agent.follow_meta_refresh = false Unsafe configuration if credentials are set in request headers agent.request_headers['Authorization'] = 'Bearer secret_token' agent.follow_meta_refresh = true
Exploit: (Educational Purposes!)
Conceptual exploitation scenario demonstrating meta refresh credential leakage
require 'mechanize'
agent = Mechanize.new
agent.follow_meta_refresh = true
agent.request_headers['Authorization'] = 'Bearer sensitive_session_token'
Agent visits an attacker-controlled page returning a meta refresh to an external origin
agent.get('http://vulnerable-crawler-target.test/page')
The request headers are automatically leaked to the attacker's server via the following meta refresh fetch
Protection: from this CVE
- Upgrade the Mechanize gem to version 2.14.1 or higher immediately.
- Ensure `Mechanizefollow_meta_refresh` remains set to its default value of `false` unless explicitly required.
- Avoid storing sensitive credentials or bearer tokens inside `Mechanizerequest_headers=` when meta refresh following is enabled.
- Implement strict egress filtering and monitor automated crawler traffic for unexpected cross-origin header transmissions.
Impact
An unauthorized remote attacker capable of placing a malicious meta refresh directive in fetched web content can successfully harvest sensitive bearer tokens, session cookies, and authentication headers set through request_headers=. This security flaw results exclusively in information disclosure with zero integrity or availability impact on the affected system.
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Sources:
Reported By: github.com
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