CVE-2026-34931: Hoppscotch Auth Bypass Vulnerability

CVE-2026-34931 Overview

CVE-2026-34931 is an open redirect vulnerability in Hoppscotch, an open source API development ecosystem. Prior to version 2026.3.0, the application contains an open redirect flaw that enables attackers to exfiltrate authentication tokens. With these stolen tokens, an attacker can authenticate as the victim and perform a complete account takeover.

Critical Impact

This vulnerability allows attackers to steal authentication tokens through open redirect manipulation, enabling full account takeover of victim users.

Affected Products

• Hoppscotch versions prior to 2026.3.0

Discovery Timeline

• 2026-04-02 - CVE-2026-34931 published to NVD
• 2026-04-02 - Last updated in NVD database

Technical Details for CVE-2026-34931

Vulnerability Analysis

This vulnerability falls under CWE-601 (URL Redirection to Untrusted Site, also known as Open Redirect). The flaw exists in Hoppscotch's redirect handling mechanism, which fails to properly validate destination URLs before redirecting users. This architectural weakness allows attackers to craft malicious URLs that appear legitimate but redirect victims to attacker-controlled domains.

The attack requires network access and user interaction, meaning victims must click on a crafted malicious link. Once triggered, the vulnerability compromises both the confidentiality and integrity of user accounts by exposing authentication tokens to unauthorized parties.

Root Cause

The root cause is improper validation of URL redirect parameters within the Hoppscotch application. The application accepts user-supplied redirect URLs without adequately verifying that the destination belongs to a trusted domain. This allows external, attacker-controlled URLs to be used as redirect targets, facilitating the exfiltration of sensitive authentication tokens that are passed during the redirect process.

Attack Vector

The attack leverages the network-based open redirect vulnerability through the following sequence:

1. An attacker crafts a malicious URL pointing to the legitimate Hoppscotch instance but with a redirect parameter pointing to an attacker-controlled server
2. The attacker distributes this link to potential victims through phishing emails, social engineering, or other delivery mechanisms
3. When a victim clicks the link and authenticates (or is already authenticated), the application redirects them to the attacker's server
4. The redirect includes authentication tokens in the URL parameters or request headers
5. The attacker captures these tokens on their malicious server
6. Using the stolen tokens, the attacker can impersonate the victim and gain full access to their Hoppscotch account

For detailed technical information about the vulnerability mechanism, refer to the GitHub Security Advisory GHSA-7fg7-wx5q-6m3v.

Detection Methods for CVE-2026-34931

Indicators of Compromise

• Unusual login activity from IP addresses not associated with legitimate users
• Authentication tokens being accessed from multiple geographic locations in short time periods
• HTTP referrer logs showing redirects to external, untrusted domains
• User reports of being redirected to unexpected websites after clicking Hoppscotch links

Detection Strategies

• Monitor web server logs for redirect requests containing external URLs in redirect parameters
• Implement anomaly detection for authentication patterns that indicate token reuse from different IP addresses
• Review access logs for suspicious referrer headers indicating users arrived from external domains
• Deploy web application firewalls (WAF) with rules to detect open redirect attack patterns

Monitoring Recommendations

• Enable detailed logging of all redirect operations within the Hoppscotch application
• Set up alerts for authentication events that follow unusual redirect patterns
• Monitor for concurrent sessions from the same user account across disparate geographic regions
• Track and analyze URL parameters in incoming requests for signs of redirect manipulation

How to Mitigate CVE-2026-34931

Immediate Actions Required

• Upgrade Hoppscotch to version 2026.3.0 or later immediately
• Review access logs for signs of exploitation or unauthorized account access
• Force re-authentication for all users and invalidate existing tokens as a precautionary measure
• Communicate with users about the vulnerability and advise them to review their account activity

Patch Information

The vulnerability has been addressed in Hoppscotch version 2026.3.0. Organizations should update to this version or later to remediate the issue. The patch implements proper URL validation to ensure redirect destinations are restricted to trusted domains only.

For patch details, see the GitHub Hoppscotch Release 2026.3.0.

Workarounds

• If immediate patching is not possible, consider implementing a reverse proxy or WAF rule to block requests with external URLs in redirect parameters
• Temporarily disable redirect functionality if operationally feasible until the patch can be applied
• Implement strict Content Security Policy headers to limit redirect destinations
• Educate users to verify URLs before clicking and to report suspicious redirect behavior

# Example WAF rule to block external redirects (adjust for your environment)
# This rule blocks redirect parameters containing external URLs
SecRule ARGS:redirect "@rx ^https?://(?!yourdomain\.com)" "id:1001,phase:1,deny,status:403,msg:'Blocked potential open redirect attempt'"