CVE-2024-53556

Executive Summary

CVE-2024-53556 is an Open Redirect vulnerability discovered in Taiga v6.8.1, a popular open-source project management platform. The flaw resides in the login page URL parameter next, which is used for post-authentication redirection. An attacker can craft a malicious link such as https://victim-taiga.example.com/login?next=https://evil.com to redirect an authenticated or unauthenticated user to an arbitrary external site after login. This can be leveraged for phishing attacks, credential harvesting, or bypassing URL validation filters.

The vulnerability has a CVSS v3.1 base score of 4.7 (Medium) due to low attack complexity, no privileges required, but requiring user interaction. No official patch has been released as of the advisory date. The EPSS score is 0.0%, indicating low exploitation probability in the wild, but the PoC is public, increasing risk for unpatched instances.

Supply Chain & Package Security

Taiga is a Python/Django-based application distributed via Docker images, PyPI packages, and source code. The vulnerability is in the core authentication module, not in a third-party dependency. However, organizations using Taiga should verify their deployment version and apply any upstream patches or workarounds immediately.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Network (N) – Exploitable remotely.
• Attack Complexity (AC): Low (L) – No special conditions required.
• Privileges Required (PR): None (N) – No authentication needed.
• User Interaction (UI): Required (R) – Victim must click the crafted link.
• Scope (S): Changed (C) – Redirect to external domain changes security scope.
• Confidentiality (C): Low (L) – Potential credential exposure via phishing.
• Integrity (I): Low (L) – Redirect can lead to malicious site.
• Availability (A): None (N) – No impact on availability.

Base Score: 4.7 (Medium)
Vector String: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Threat Level: Medium – Public PoC exists, but no active exploitation observed. Risk increases if Taiga is exposed to the internet.

Deep Dive & Mechanics

The vulnerability is a classic open redirect in the Django-based Taiga application. The login endpoint at /login?next= accepts a URL parameter next that specifies where the user should be redirected after successful authentication. The application fails to validate that the redirect target is within the same origin or a trusted domain.

Attack Flow:

1. Attacker crafts a URL: https://taiga.example.com/login?next=https://evil.com/phish
2. Victim clicks the link (e.g., via email or social engineering).
3. Victim is presented with the legitimate Taiga login page.
4. After entering credentials, the browser redirects to https://evil.com/phish.
5. The attacker can now harvest credentials or serve malware.

Root Cause: The next parameter is not sanitized or validated against a whitelist of allowed domains. Django’s django.utils.http.is_safe_url or similar validation is either missing or improperly implemented.

Vulnerable vs. Patched Code

Vulnerable Code (Taiga v6.8.1):

# In login view (simplified)
def login_view(request):
    next_url = request.GET.get('next', '/')
    # No validation of next_url
    return redirect(next_url)

Patched Code (Hypothetical fix):

from django.utils.http import is_safe_url

def login_view(request):
    next_url = request.GET.get('next', '/')
    if not is_safe_url(next_url, allowed_hosts={request.get_host()}):
        next_url = '/'
    return redirect(next_url)

Key Difference: The patched version uses is_safe_url to ensure the redirect target is within the same host, preventing open redirects.

Exploitation & Lab Setup

Red Team (Attacker)

Prerequisites:

• A publicly accessible Taiga instance (e.g., http://target-taiga:8000).
• A controlled external server (e.g., http://attacker.com).

Exploit Steps:

1. Craft the malicious URL:

   http://target-taiga:8000/login?next=http://attacker.com/steal
   

2. Send the link to the victim via phishing email or social media.
3. Victim clicks, logs in, and is redirected to http://attacker.com/steal.
4. On the attacker server, host a fake login page or capture credentials.

Proof-of-Concept (PoC) Script:

import requests

target = "http://target-taiga:8000"
malicious_url = "http://attacker.com/steal"

# Craft the redirect URL
redirect_url = f"{target}/login?next={malicious_url}"
print(f"Send this link to victim: {redirect_url}")

# Simulate a victim clicking (optional)
response = requests.get(redirect_url, allow_redirects=False)
print(f"Redirect status: {response.status_code}")
print(f"Location header: {response.headers.get('Location')}")

Blue Team (Defender)

Detection Steps:

1. Monitor logs for unusual next parameter values in login requests.
2. Check for external domains in the Referer header after login.
3. Use the detection rules below to identify exploitation attempts.

Mitigation Workarounds (if no patch):

• Implement a reverse proxy (e.g., Nginx) to block next parameters containing external domains.
• Modify the application code to validate the next parameter against a whitelist.
• Disable the next parameter entirely if not needed.

Indicators of Compromise (IOCs)

• URL Pattern: /login?next=http:// or /login?next=https:// with external domains.
• Log Entries: GET /login?next=http://evil.com with status 302 and Location: http://evil.com.
• Network Traffic: Outbound connections to unknown domains immediately after login requests.
• User Agent: No specific UA, but unusual referrers or repeated login attempts.

Detection Engineering

YARA Rule

rule CVE_2024_53556_Open_Redirect {
    meta:
        description = "Detects open redirect attempts in Taiga login URLs"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-53556"
    strings:
        $login_path = "/login?next="
        $external_domain = /next=https?:\/\/[^\/]+\.[a-z]{2,}/
    condition:
        $login_path and $external_domain
}

Sigma Rule

title: Taiga Open Redirect via login?next Parameter
id: 8a9b3c4d-5e6f-7a8b-9c0d-1e2f3a4b5c6d
status: experimental
description: Detects HTTP requests to Taiga login with external redirect targets
author: Valters IT
logsource:
    category: webserver
    product: apache
    service: access_log
detection:
    selection:
        cs-uri-query|contains: "/login?next="
        cs-uri-query|re: "next=https?://[^/]+\.[a-z]{2,}"
    condition: selection
falsepositives:
    - Legitimate external redirects if configured
level: medium

Suricata Rule

alert http any any -> any any (msg:"CVE-2024-53556 Taiga Open Redirect Attempt"; flow:to_server,established; content:"/login?next="; http_uri; pcre:"/next=https?:\/\/[^\/]+\.[a-z]{2,}/Ri"; classtype:attempted-recon; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate Action: If using Taiga v6.8.1, apply the following workaround in your reverse proxy (Nginx example):

   location /login {
       if ($arg_next ~* "^https?://") {
           return 403;
       }
       proxy_pass http://taiga-backend;
   }
   

2. Code Fix: Add validation for the next parameter using Django’s is_safe_url or a custom whitelist.
3. Upgrade: Monitor Taiga’s official repository for a patched version and upgrade immediately.
4. User Awareness: Educate users not to click suspicious links and to verify URLs before logging in.

Valters IT
Senior DevSecOps & Cyber Threat Intelligence Analyst
Report generated for CVE-2024-53556