CVE-2026-3216: Drupal Canvas SSRF Vulnerability

CVE-2026-3216 Overview

A Server-Side Request Forgery (SSRF) vulnerability has been identified in the Drupal Canvas module. This vulnerability allows authenticated attackers to make arbitrary HTTP requests from the server, potentially accessing internal resources, services, or sensitive information that should not be externally accessible. The vulnerability affects Drupal Canvas versions from 0.0.0 before 1.1.1.

Critical Impact

Attackers with low-privilege access can exploit this SSRF vulnerability to probe internal network infrastructure, access cloud metadata endpoints, or pivot to internal services not exposed to the public internet.

Affected Products

• Drupal Canvas versions 0.0.0 to 1.1.0
• Drupal sites running vulnerable Drupal Canvas module versions

Discovery Timeline

• 2026-03-25 - CVE CVE-2026-3216 published to NVD
• 2026-03-26 - Last updated in NVD database

Technical Details for CVE-2026-3216

Vulnerability Analysis

This SSRF vulnerability (CWE-918) in Drupal Canvas allows an authenticated attacker to manipulate the server into making HTTP requests to arbitrary destinations. The vulnerability requires network access and low-privilege authentication to exploit, with no user interaction needed.

The attack enables unauthorized access to internal resources by leveraging the server as a proxy. While the immediate impact is limited to confidentiality exposure (read-only access to internal data), the vulnerability can serve as a reconnaissance tool or stepping stone for more sophisticated attacks against internal infrastructure.

Root Cause

The vulnerability stems from insufficient validation of user-supplied URLs or request parameters within the Drupal Canvas module. When the module processes external resource requests, it fails to properly sanitize or restrict the destination URLs, allowing attackers to specify arbitrary internal or external endpoints.

Attack Vector

The attack is conducted over the network by an authenticated user with low privileges. The attacker crafts malicious requests that manipulate URL parameters or input fields processed by the Drupal Canvas module. The server then makes requests to attacker-specified destinations, potentially exposing:

• Internal network services (e.g., databases, admin panels)
• Cloud provider metadata endpoints (e.g., 169.254.169.254)
• Local services bound to 127.0.0.1
• Internal APIs and microservices

The vulnerability manifests when the Drupal Canvas module processes external resource references without proper URL validation or allowlist enforcement. Attackers can manipulate input parameters to redirect server-side requests to internal resources. For detailed technical information, see the Drupal Security Advisory.

Detection Methods for CVE-2026-3216

Indicators of Compromise

• Unusual outbound HTTP requests from the Drupal web server to internal IP ranges (10.x.x.x, 172.16.x.x, 192.168.x.x)
• Requests to cloud metadata endpoints such as 169.254.169.254 originating from the web server
• HTTP requests to localhost or 127.0.0.1 from server-side processes
• Anomalous DNS queries for internal hostnames from the web application tier

Detection Strategies

• Monitor web server egress traffic for connections to internal network ranges or metadata services
• Implement application-layer logging to capture URL parameters passed to the Drupal Canvas module
• Deploy web application firewall (WAF) rules to detect SSRF patterns in request parameters
• Enable audit logging for Drupal module activity to track suspicious resource requests

Monitoring Recommendations

• Configure network monitoring to alert on outbound connections from web servers to internal services
• Implement DNS logging to detect resolution of internal hostnames by the web application
• Review Drupal watchdog logs for error messages related to failed internal resource access attempts
• Set up alerts for requests containing internal IP addresses or localhost references in URL parameters

How to Mitigate CVE-2026-3216

Immediate Actions Required

• Upgrade Drupal Canvas module to version 1.1.1 or later immediately
• Review server access logs for indicators of SSRF exploitation attempts
• Audit network egress rules to restrict unnecessary outbound connections from web servers
• Consider temporarily disabling the Drupal Canvas module if immediate patching is not feasible

Patch Information

The vulnerability has been addressed in Drupal Canvas version 1.1.1. Administrators should upgrade to this version or later to remediate the SSRF vulnerability. Detailed patch information and upgrade instructions are available in the Drupal Security Advisory.

Workarounds

• Implement network-level restrictions to prevent the web server from accessing internal resources
• Configure firewall rules to block outbound connections to private IP ranges and metadata endpoints
• Deploy a web application firewall with SSRF detection rules to filter malicious requests
• Use URL allowlisting at the application level to restrict which external resources can be accessed

# Example firewall rules to block common SSRF targets
# Block access to cloud metadata endpoints
iptables -A OUTPUT -d 169.254.169.254 -j DROP

# Block access to private IP ranges from web server
iptables -A OUTPUT -d 10.0.0.0/8 -j DROP
iptables -A OUTPUT -d 172.16.0.0/12 -j DROP
iptables -A OUTPUT -d 192.168.0.0/16 -j DROP
iptables -A OUTPUT -d 127.0.0.0/8 -j DROP