CVE-2025-61166 Overview
An open redirect vulnerability exists in Ascertia SigningHub User v10.0 that allows attackers to redirect users to a malicious site via a crafted URL. This type of vulnerability (CWE-601) occurs when a web application accepts user-controlled input that specifies a link to an external site and uses that link in a redirect without proper validation.
Critical Impact
Attackers can leverage this vulnerability to conduct phishing attacks by creating malicious URLs that appear to originate from the trusted SigningHub domain, potentially leading to credential theft or malware distribution.
Affected Products
- Ascertia SigningHub User v10.0
Discovery Timeline
- 2026-04-06 - CVE CVE-2025-61166 published to NVD
- 2026-04-07 - Last updated in NVD database
Technical Details for CVE-2025-61166
Vulnerability Analysis
This open redirect vulnerability in Ascertia SigningHub User v10.0 allows attackers to craft malicious URLs that, when clicked by a victim, redirect them from the legitimate SigningHub application to an attacker-controlled website. The vulnerability exploits insufficient validation of URL parameters used in redirect operations within the application.
Open redirect vulnerabilities are particularly dangerous in document signing platforms like SigningHub because users inherently trust URLs from these services. When a user receives what appears to be a legitimate signing request or notification link, they are more likely to click through without scrutinizing the final destination, making this an effective vector for phishing campaigns.
Root Cause
The vulnerability stems from improper URL validation in the SigningHub User application's redirect handling mechanism. The application fails to adequately verify that the target URL in redirect parameters points to a trusted destination, allowing attackers to inject arbitrary external URLs that the application will redirect users to without warning.
Attack Vector
The attack is executed over the network and requires user interaction—specifically, a victim must click on the malicious crafted URL. Attackers typically distribute these URLs through phishing emails, social media, or other communication channels, disguising them as legitimate SigningHub links. When clicked, the user's browser follows the redirect from the trusted SigningHub domain to the attacker's malicious site.
The attack flow typically involves:
- Attacker crafts a URL containing the SigningHub domain with a malicious redirect parameter
- Victim clicks the link, believing it to be legitimate
- SigningHub application processes the request and redirects to the attacker-controlled site
- Attacker's site may harvest credentials, serve malware, or conduct further social engineering
For detailed technical analysis, refer to the Medium Article on CVE-2025-61166.
Detection Methods for CVE-2025-61166
Indicators of Compromise
- URLs containing the SigningHub domain with suspicious redirect parameters pointing to external domains
- User complaints about being redirected to unexpected websites after clicking SigningHub links
- Web server logs showing requests with external URLs in redirect-related query parameters
Detection Strategies
- Monitor web application logs for requests containing redirect parameters with external domain values
- Implement URL analysis tools to identify SigningHub URLs with suspicious redirect destinations before user interaction
- Deploy email gateway rules to flag or quarantine emails containing SigningHub URLs with unusual query parameters
Monitoring Recommendations
- Review web proxy logs for unusual redirect patterns originating from SigningHub application URLs
- Implement real-time alerting for high volumes of redirect requests to newly registered or low-reputation domains
- Educate users to report suspicious redirect behavior when interacting with SigningHub links
How to Mitigate CVE-2025-61166
Immediate Actions Required
- Review and audit all SigningHub URL parameters for potential redirect abuse
- Implement URL allowlisting for redirect destinations within the SigningHub application
- Educate users about the risks of clicking on unexpected or suspicious SigningHub links
- Consider deploying web filtering to block known malicious redirect destinations
Patch Information
No vendor-issued patch information is currently available in the CVE data. Organizations should monitor Ascertia's security advisories for updates regarding SigningHub User v10.0. Contact Ascertia support for guidance on available fixes or updated versions that address this vulnerability.
Workarounds
- Implement strict URL validation and allowlisting for all redirect parameters at the web application firewall level
- Configure web proxies to inspect and block requests with external redirect destinations in SigningHub URLs
- Train users to manually navigate to SigningHub rather than clicking links in emails or messages
- Deploy browser extensions or endpoint protection that warns users before following redirects to untrusted domains
Organizations should implement a redirect validation mechanism that restricts redirects to approved internal paths or explicitly allowlisted external domains only.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
