CVE-2026-31878: Frappe Framework SSRF Vulnerability

CVE-2026-31878 Overview

CVE-2026-31878 is a Server-Side Request Forgery (SSRF) vulnerability discovered in Frappe, a full-stack web application framework. Prior to versions 14.100.1, 15.100.0, and 16.6.0, a malicious user could send a crafted request to an endpoint which would lead to the server making an HTTP call to a service of the user's choice. This vulnerability allows authenticated attackers to abuse the server as a proxy to reach internal services or external destinations that would otherwise be inaccessible.

Critical Impact

Authenticated attackers can leverage this SSRF vulnerability to scan internal networks, access internal services, exfiltrate sensitive data, or potentially pivot to other attack vectors within the target infrastructure.

Affected Products

• Frappe Framework versions prior to 14.100.1
• Frappe Framework versions prior to 15.100.0
• Frappe Framework versions prior to 16.6.0

Discovery Timeline

• 2026-03-11 - CVE-2026-31878 published to NVD
• 2026-03-12 - Last updated in NVD database

Technical Details for CVE-2026-31878

Vulnerability Analysis

This SSRF vulnerability (CWE-918) exists in Frappe's web application framework where an endpoint fails to properly validate user-controlled URL parameters before making outbound HTTP requests. The vulnerability requires low-privilege authentication to exploit, meaning any authenticated user can potentially abuse this flaw.

When a malicious user submits a crafted request containing an arbitrary URL, the Frappe server blindly follows the URL and makes an HTTP call to the specified destination. This behavior can be exploited to interact with internal services that are not directly accessible from the internet, such as metadata endpoints in cloud environments, internal APIs, or other backend services.

The scope of this vulnerability extends beyond the vulnerable component itself, as the attacker can potentially access resources in other security domains. However, the impact is limited to information disclosure since the vulnerability only allows reading data from the targeted services, not modifying or executing code on them.

Root Cause

The root cause of this vulnerability is insufficient validation of user-supplied URL parameters in Frappe's request handling logic. The application accepts arbitrary URLs from authenticated users and makes HTTP requests to those URLs without properly restricting the target destinations. This lack of URL allowlisting or blocklisting allows attackers to specify internal IP addresses, localhost services, or cloud metadata endpoints as targets.

Attack Vector

The attack is network-based and requires the attacker to have low-privilege authentication to the Frappe application. No user interaction is required to exploit this vulnerability. An attacker would craft a malicious request containing an internal URL (such as http://169.254.169.254/ for cloud metadata services or http://localhost:port/ for internal services) and submit it to the vulnerable endpoint.

The vulnerability mechanism involves the server-side component processing the attacker-controlled URL and making an outbound HTTP request. The response from the internal service is then potentially returned to the attacker or used in a way that leaks information. For detailed technical analysis and exploitation specifics, refer to the GitHub Security Advisory.

Detection Methods for CVE-2026-31878

Indicators of Compromise

• Outbound HTTP requests from the Frappe server to unexpected internal IP ranges (e.g., 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16)
• HTTP requests to cloud metadata endpoints such as 169.254.169.254 originating from the web application
• Unusual outbound connections to localhost or loopback addresses from the Frappe application process
• Log entries showing requests to internal services that should not be accessible from the web application layer

Detection Strategies

• Implement network monitoring to detect outbound connections from web application servers to internal IP ranges or metadata endpoints
• Configure Web Application Firewall (WAF) rules to identify and block SSRF attack patterns in request parameters
• Enable verbose logging on the Frappe application to capture all outbound HTTP requests and their destinations
• Deploy SentinelOne Singularity XDR to detect anomalous network behavior from application servers

Monitoring Recommendations

• Monitor egress traffic from Frappe application servers for connections to internal network segments
• Set up alerts for HTTP requests to well-known metadata endpoints (169.254.169.254, fd00:ec2::254)
• Review application logs for unusual URL patterns in request parameters
• Implement network segmentation monitoring to detect lateral movement attempts

How to Mitigate CVE-2026-31878

Immediate Actions Required

• Upgrade Frappe Framework to version 14.100.1, 15.100.0, or 16.6.0 or later immediately
• Audit logs for evidence of exploitation attempts targeting internal services
• Review network segmentation to ensure the Frappe application server cannot reach sensitive internal services
• Implement egress filtering to restrict outbound HTTP requests from the application server

Patch Information

The Frappe development team has released security patches addressing this SSRF vulnerability. Users should upgrade to the following fixed versions:

• Version 14.100.1 for the 14.x branch
• Version 15.100.0 for the 15.x branch
• Version 16.6.0 for the 16.x branch

For additional details and patch information, consult the GitHub Security Advisory.

Workarounds

• Implement a Web Application Firewall (WAF) rule to block requests containing internal IP addresses or localhost references in URL parameters
• Configure network-level egress filtering to prevent the Frappe application server from making requests to internal IP ranges
• If possible, place the Frappe application in an isolated network segment with restricted outbound connectivity
• Disable or restrict access to the vulnerable endpoint if the functionality is not critical for business operations

# Example iptables rules to restrict outbound connections from the Frappe server
# Block access to common internal IP ranges from the web application
iptables -A OUTPUT -m owner --uid-owner frappe -d 10.0.0.0/8 -j DROP
iptables -A OUTPUT -m owner --uid-owner frappe -d 172.16.0.0/12 -j DROP
iptables -A OUTPUT -m owner --uid-owner frappe -d 192.168.0.0/16 -j DROP
iptables -A OUTPUT -m owner --uid-owner frappe -d 169.254.169.254 -j DROP