CVE-2023-24034 in Nagios
Summary
by MITRE • 09/14/2026
An issue was discovered in twilio_ajax_handler.php in Nagios XI before 5.9.3. An attacker can force a user to visit a malicious site by using a open redirect vulnerability.
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Analysis
by VulDB Data Team • 09/14/2026
The identified vulnerability resides within the twilio_ajax_handler.php component of Nagios XI versions prior to release 5.9.3, representing an Open Redirect flaw that allows attackers to manipulate URL redirection logic for social engineering purposes. This specific type of weakness is formally categorized under CWE-601 in the Common Weakness Enumeration standard, which defines open redirects as a failure to properly validate user-supplied input before using it to redirect users to another location. In this context, the application accepts external parameters that dictate where the system should send the authenticated user after an action or authentication event is completed. Because the validation mechanism for these destination URLs is insufficient, an attacker can craft a malicious link containing a legitimate-looking base URL from Nagios XI followed by a redirect parameter pointing to a phishing site controlled by the adversary.
The operational impact of this vulnerability centers on its utility as a vector for social engineering attacks rather than direct system compromise or data exfiltration through code execution. By exploiting this flaw, an attacker can create URLs that appear to originate from the trusted Nagios XI domain, thereby bypassing user skepticism regarding link safety. When a victim clicks such a link, they are seamlessly redirected away from the monitoring platform and onto a malicious website designed to mimic legitimate login pages or other critical interfaces. This deception facilitates credential harvesting, where users unknowingly submit their usernames and passwords to the attacker. Furthermore, this redirect capability can be leveraged in phishing campaigns to distribute malware or trick users into performing unauthorized administrative actions within the Nagios XI environment if they believe they are still interacting with the authentic application interface.
From a tactical perspective, this vulnerability aligns with techniques observed in adversary behavior models such as MITRE ATT&CK technique T1566.002, which covers Spearphishing Link attacks where attackers send links to phishing sites that mimic trusted entities. The effectiveness of this attack relies heavily on the trust users place in URLs originating from their internal infrastructure tools like Nagios XI. Since monitoring systems are critical for operational visibility and often contain sensitive configuration data or administrative controls, compromising user credentials through such redirects can serve as an initial access vector for more severe intrusions. Once attackers obtain valid credentials via this redirect-based phishing scheme, they may proceed to escalate privileges, exfiltrate network topology information, or disrupt service monitoring capabilities depending on the permissions associated with the compromised account.
Mitigation strategies must prioritize immediate patching and defensive configuration changes to address both the root cause and potential exploitation vectors. The primary remediation step is to upgrade Nagios XI to version 5.9.3 or later, where this specific open redirect flaw in twilio_ajax_handler.php has been resolved through improved input validation and strict allow-listing of permitted redirection targets. In environments where immediate patching is not feasible due to operational constraints, administrators should implement web application firewall rules that detect and block requests containing suspicious query parameters associated with known open redirect patterns. Additionally, user awareness training plays a crucial role in defense-in-depth; employees should be educated to verify the exact destination of links even if they appear to originate from trusted internal domains, as attackers can easily spoof these origins using this vulnerability. Regular security audits focusing on authentication flows and redirection logic across all web components will help identify similar weaknesses before they are exploited by malicious actors seeking initial access through social engineering tactics.