CVE-2017-1000481 in Plone
Summary
by MITRE
When you visit a page where you need to login, Plone 2.5-5.1rc1 sends you to the login form with a 'came_from' parameter set to the previous url. After you login, you get redirected to the page you tried to view before. An attacker might try to abuse this by letting you click on a specially crafted link. You would login, and get redirected to the site of the attacker, letting you think that you are still on the original Plone site. Or some javascript of the attacker could be executed. Most of these types of attacks are already blocked by Plone, using the `isURLInPortal` check to make sure we only redirect to a page on the same Plone site. But a few more ways of tricking Plone into accepting a malicious link were discovered, and fixed with this hotfix.
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Analysis
by VulDB Data Team • 12/19/2019
This vulnerability represents a critical open redirect issue affecting Plone content management systems version 2.5 through 5.1rc1, specifically targeting the authentication redirect mechanism that utilizes the 'came_from' parameter. The flaw exploits the legitimate redirect functionality designed to return users to their originally requested page after successful authentication, creating a pathway for malicious redirection attacks that bypass existing security controls. The vulnerability operates by manipulating the URL validation process that should restrict redirects to the same Plone site, demonstrating a failure in the isURLInPortal check implementation that was intended to prevent cross-site redirection attacks.
The technical implementation of this vulnerability stems from insufficient input validation and URL parsing within Plone's authentication flow. When users attempt to access protected resources, the system stores the requested URL in the came_from parameter and performs validation using the isURLInPortal function. However, attackers can craft malicious URLs that exploit edge cases in the validation logic, allowing them to redirect authenticated users to attacker-controlled domains while maintaining the illusion of staying within the legitimate Plone environment. This type of vulnerability aligns with CWE-601 Open Redirect, where applications redirect users to untrusted domains without sufficient validation. The attack vector specifically targets the URL parsing and validation routines that should prevent such redirections, creating a security boundary failure that enables phishing and social engineering attacks.
The operational impact of this vulnerability extends beyond simple redirection, as it enables sophisticated attack scenarios including credential harvesting, malicious code execution through JavaScript injection, and phishing campaigns that can deceive users into believing they remain on legitimate Plone sites. Users who authenticate through compromised links may unknowingly execute attacker-controlled JavaScript or navigate to malicious domains that appear to be part of the original Plone installation. This creates a significant risk for organizations relying on Plone for sensitive content management, as the vulnerability can be exploited through various attack vectors including email phishing, compromised website links, or social engineering campaigns. The vulnerability particularly affects web applications that depend on user authentication flows and redirect mechanisms, making it a critical concern for enterprise content management systems.
Mitigation strategies for this vulnerability require immediate implementation of the official hotfix provided by Plone developers, which strengthens the URL validation logic and addresses the specific edge cases in the isURLInPortal check. Organizations should also implement additional security measures including comprehensive URL validation routines, strict referer header checks, and enhanced monitoring of authentication redirect patterns. The solution involves updating the Plone core authentication module to properly validate URLs against the site's domain, ensuring that all redirect destinations are strictly validated against the configured portal root and that relative URLs are properly resolved. Security teams should also consider implementing web application firewalls with specific rules to detect and block suspicious redirect patterns, and conduct regular security assessments to identify potential similar vulnerabilities in other authentication mechanisms. This vulnerability demonstrates the critical importance of proper input validation and the need for defense-in-depth approaches to protect authentication flows from manipulation attacks that can compromise user security and trust in web applications.