CVE-2026-120327 in Mail
Summary
by MITRE • 11/03/2026
The click tracking middleware accepts an arbitrary target URL and redirects to it. Attackers can misuse links to the website to redirect users to external sites.
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Analysis
by VulDB Data Team • 11/03/2026
This vulnerability represents a classic Open Redirect flaw, specifically occurring within a click tracking middleware component of a web application or service. The core technical deficiency lies in the insufficient validation of user-supplied input used as the destination for an HTTP redirection response. When a system accepts an arbitrary target URL and immediately issues a redirect without verifying that the domain matches expected internal domains or is on a predefined allowlist, it creates a pathway for attackers to manipulate the navigation flow. This behavior violates fundamental security principles regarding trust boundaries, as the application treats untrusted external input with the same level of authority as trusted internal configuration data.
The operational impact of this vulnerability extends beyond simple misdirection and can be leveraged for sophisticated social engineering attacks. By crafting a malicious link that appears to originate from the legitimate website due to its use of the official domain in the URL path, attackers can deceive users into believing they are still on the trusted platform. This deception is particularly dangerous when used in phishing campaigns where victims are redirected to a high-fidelity replica of a login page hosted on an external server. Once the user enters their credentials or sensitive personal information on this fraudulent site, the attacker captures these details for subsequent unauthorized access and identity theft.
From a classification perspective, this issue aligns directly with CWE-601, which defines URL Redirection to Untrusted Site (Open Redirect). It also maps effectively to the MITRE ATT&CK framework under technique T1583, specifically subtechnique T1583.002 for Acquiring Infrastructure: Domains, as attackers often register domains that mimic legitimate ones to facilitate these redirects. Furthermore, it relates to CWE-469 if the redirect logic relies on a lack of restriction in an inherited class or middleware configuration, and CWE-79 if the redirected page contains malicious scripts, although the primary vector here is the redirection itself rather than direct script injection within the vulnerable parameter.
Mitigation strategies must focus on strict input validation and secure coding practices for handling redirects. The most effective approach is to implement a whitelist-based verification system where only pre-approved domains or specific URL patterns are permitted as redirect targets. If dynamic domain resolution is required, developers should validate that the resolved IP address does not point to private network ranges or known malicious hosts using tools like DNSBLs. Additionally, avoiding direct user input in location headers and instead mapping short codes or identifiers to internal routes can eliminate this risk entirely. Security testing procedures should include automated scans for open redirect vulnerabilities by injecting various URL formats into target parameters and verifying that the application does not perform unauthorized external redirections.