CVE-2025-45286: Httpbingo Go-httpbin XSS Vulnerability

CVE-2025-45286 Overview

A cross-site scripting (XSS) vulnerability exists in mccutchen httpbin v2.17.1 that allows attackers to execute arbitrary web scripts or HTML via a crafted payload. This vulnerability affects the go-httpbin project, which is a Go implementation of the popular httpbin HTTP request and response service.

Critical Impact

Attackers can inject malicious scripts that execute in the context of a user's browser session, potentially leading to session hijacking, credential theft, or malicious actions performed on behalf of authenticated users.

Affected Products

• httpbingo go-httpbin
• mccutchen httpbin v2.17.1
• Go-based httpbin deployments using vulnerable versions

Discovery Timeline

• 2026-01-02 - CVE-2025-45286 published to NVD
• 2026-01-07 - Last updated in NVD database

Technical Details for CVE-2025-45286

Vulnerability Analysis

This vulnerability is classified as CWE-80 (Improper Neutralization of Script-Related HTML Tags in a Web Page), which represents a specific type of cross-site scripting flaw. The go-httpbin application fails to properly sanitize user-supplied input before reflecting it back in HTTP responses. This allows attackers to craft malicious payloads containing JavaScript or HTML that will be executed in the victim's browser when they interact with a specially crafted URL or request.

The attack requires user interaction, as victims must be tricked into clicking a malicious link or visiting a compromised page that targets the vulnerable httpbin instance. However, since httpbin services are commonly used for testing and development purposes, they may be exposed on internal networks or even public-facing environments, increasing the potential attack surface.

Root Cause

The root cause of this vulnerability lies in improper input validation and output encoding within the go-httpbin application. Specifically, user-controlled input is reflected in HTTP responses without adequate sanitization of HTML special characters or script tags. The application fails to implement proper output encoding that would neutralize potentially malicious script content before it reaches the browser.

Attack Vector

This vulnerability is exploitable over the network and requires user interaction. An attacker can craft a malicious URL containing JavaScript payload that, when clicked by a victim, executes arbitrary scripts in their browser context. The attack leverages the trust relationship between the user's browser and the httpbin service.

The exploitation flow typically involves:

1. Attacker identifies a vulnerable go-httpbin instance
2. Attacker crafts a malicious URL with XSS payload
3. Victim is tricked into clicking the malicious link
4. The vulnerable endpoint reflects the payload without sanitization
5. Malicious script executes in victim's browser with the origin of the httpbin service

Due to the reflected nature of this XSS vulnerability, the payload is delivered through the request and immediately rendered in the response. Technical details and proof-of-concept information may be available in the GitHub Security Advisory.

Detection Methods for CVE-2025-45286

Indicators of Compromise

• Unusual URL patterns containing encoded script tags or JavaScript event handlers in requests to httpbin endpoints
• HTTP access logs showing requests with HTML/JavaScript special characters (<script>, onerror=, onload=, etc.)
• Reports from users experiencing unexpected browser behavior when accessing httpbin services
• Web Application Firewall (WAF) alerts for XSS pattern matches targeting httpbin paths

Detection Strategies

• Deploy Web Application Firewall rules to detect and block common XSS payloads in requests to httpbin services
• Implement Content Security Policy (CSP) headers to mitigate the impact of successful XSS attacks
• Monitor HTTP access logs for suspicious patterns indicative of XSS probing or exploitation attempts
• Use automated vulnerability scanners to identify exposed go-httpbin instances running version v2.17.1

Monitoring Recommendations

• Enable verbose logging on httpbin instances to capture full request details for forensic analysis
• Configure alerting for requests containing common XSS vectors such as <script>, javascript:, or HTML event attributes
• Implement rate limiting to detect and slow down automated scanning or exploitation attempts
• Review Content Security Policy violation reports for signs of attempted script injection

How to Mitigate CVE-2025-45286

Immediate Actions Required

• Identify all go-httpbin deployments in your environment running version v2.17.1 or earlier
• Restrict network access to httpbin instances to trusted networks or users only
• Implement Web Application Firewall rules to filter known XSS patterns
• Consider temporarily disabling public access to vulnerable httpbin services until patched

Patch Information

Refer to the official GitHub Security Advisory GHSA-528q-4pgm-wvg2 for the latest patch information and recommended upgrade path. Organizations should upgrade to the latest version of go-httpbin that addresses this vulnerability as soon as patches become available.

Workarounds

• Place vulnerable httpbin instances behind a reverse proxy with XSS filtering capabilities
• Implement strict Content Security Policy headers to prevent inline script execution
• Restrict access to httpbin services using network segmentation or authentication mechanisms
• Consider using alternative HTTP testing services until the vulnerability is patched

# Example: Add CSP headers via nginx reverse proxy
# Add to nginx server configuration for httpbin
add_header Content-Security-Policy "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline';" always;
add_header X-Content-Type-Options "nosniff" always;
add_header X-XSS-Protection "1; mode=block" always;