CVE-2024-33661: Portainer Open Redirect Vulnerability

CVE-2024-33661 Overview

CVE-2024-33661 is an Open Redirect vulnerability (CWE-601) affecting Portainer, a popular container management platform, in versions prior to 2.20.0. The vulnerability allows attackers to craft malicious URLs that redirect users to arbitrary external destinations when the target is not index.yaml. This type of vulnerability is commonly exploited in phishing attacks and credential theft campaigns, as users may trust URLs that appear to originate from legitimate Portainer instances.

Critical Impact

This vulnerability enables attackers to redirect authenticated Portainer users to malicious websites, potentially facilitating credential harvesting, malware distribution, or session hijacking attacks against container management infrastructure.

Affected Products

• Portainer versions prior to 2.20.0
• All Portainer deployments exposed to network access without proper URL validation
• Container management environments utilizing vulnerable Portainer instances

Discovery Timeline

• 2024-04-26 - CVE-2024-33661 published to NVD
• 2025-05-21 - Last updated in NVD database

Technical Details for CVE-2024-33661

Vulnerability Analysis

This Open Redirect vulnerability exists in Portainer's URL handling mechanism, specifically in how the application processes redirect requests. The flaw occurs because the application fails to properly validate redirect targets when the destination is not index.yaml. This insufficient validation allows an attacker to manipulate redirect parameters to point users to external, potentially malicious domains.

The vulnerability is exploitable over the network without requiring authentication or user interaction beyond clicking a crafted link. Successful exploitation can lead to significant confidentiality and integrity impacts, as attackers can leverage trusted Portainer URLs to deceive users into visiting attacker-controlled sites.

Root Cause

The root cause of CVE-2024-33661 is improper input validation in Portainer's redirect handling logic. The application implemented a condition that only validates redirects when the target is index.yaml, leaving all other redirect targets unchecked. This creates a bypass condition where attackers can specify arbitrary URLs as redirect destinations, as long as they don't match the index.yaml pattern.

Attack Vector

The attack vector for this vulnerability is network-based, requiring no privileges or user interaction beyond visiting a malicious link. An attacker can exploit this vulnerability by:

1. Crafting a URL to a vulnerable Portainer instance with a malicious redirect parameter
2. Distributing the crafted URL through phishing emails, social engineering, or compromised websites
3. When a user clicks the link, they are redirected from the trusted Portainer domain to an attacker-controlled site
4. The attacker can then present fake login pages, malware downloads, or other malicious content

This attack is particularly effective because the initial URL appears to be legitimate, potentially including valid Portainer instance domains that users trust.

Detection Methods for CVE-2024-33661

Indicators of Compromise

• Unusual redirect patterns in Portainer access logs pointing to external domains
• User reports of being redirected to unexpected websites after clicking Portainer links
• Presence of URL parameters containing external domain references in web server logs
• Phishing attempts leveraging your organization's Portainer instance URLs

Detection Strategies

• Monitor web application firewall (WAF) logs for redirect attempts to external domains
• Implement URL inspection rules to detect redirect parameter manipulation
• Review Portainer access logs for requests containing suspicious redirect parameters
• Deploy network monitoring to detect outbound redirects from Portainer instances to untrusted domains

Monitoring Recommendations

• Configure alerting for any Portainer requests containing redirect parameters pointing outside your domain
• Implement logging for all URL redirection events within Portainer
• Monitor for increased phishing activity that may leverage your Portainer infrastructure
• Track user session patterns for anomalous redirect behavior

How to Mitigate CVE-2024-33661

Immediate Actions Required

• Upgrade Portainer to version 2.20.0 or later immediately
• Review access logs for evidence of exploitation attempts
• Alert users about potential phishing attempts using Portainer URLs
• Implement network-level URL filtering to block known malicious redirect destinations

Patch Information

The vulnerability has been addressed in Portainer version 2.20.0. The fix was implemented through Pull Request #11233 and Pull Request #11236 on GitHub. Organizations should upgrade to version 2.20.0 or later to remediate this vulnerability. For a complete list of changes between versions, refer to the GitHub comparison between versions 2.19.4 and 2.20.0.

Workarounds

• Deploy a web application firewall (WAF) with rules to block requests containing external redirect parameters
• Implement network segmentation to limit Portainer exposure to trusted networks only
• Use reverse proxy configurations to validate and sanitize redirect parameters before forwarding to Portainer
• Educate users about verifying URLs before entering credentials, even on trusted domains

# Example: Nginx reverse proxy configuration to block external redirects
location /portainer/ {
    # Block requests with external redirect parameters
    if ($args ~* "redirect=https?://(?!your-domain\.com)") {
        return 403;
    }
    proxy_pass http://portainer:9000/;
    proxy_set_header Host $host;
    proxy_set_header X-Real-IP $remote_addr;
}