The recent revelation of CVE-2024-21893 has underscored the urgent need for serious security measures. This server-side request forgery (SSRF) vulnerability in the Security Assertion Markup Language (SAML) component of Ivanti Connect Secure and Policy Secure appliances is a stark reminder of the sophistication of cyber threats. Rapid7’s insightful analysis has been instrumental in shedding light on this vulnerability, emphasizing the critical importance of immediate and informed action.
A Technical Overview
CVE-2024-21893, as disclosed by Ivanti, represents a significant security risk, allowing attackers to bypass authentication mechanisms through a server-side request forgery (SSRF) in the SAML component. This vulnerability is part of a complex web of security challenges, initially exposed through an authentication bypass vulnerability (CVE-2023-46805) and a command injection vulnerability (CVE-2024-21887). These vulnerabilities were initially mitigated by Ivanti; however, the discovery of CVE-2024-21893 introduced a new method for attackers to exploit these systems.
Exploit Characteristics
| CVE ID | CVE-2024-21893 |
| CWE ID | CWE-918: Server-Side Request Forgery (SSRF) |
| Impact | High |
| Likelihood | Medium |
| Severity | 8.2 (High) |
| CVSS Score | 8.2 AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N |
| Exploitability | Functional exploitation is possible with no specific privileges required. |
| Impact Analysis | Unauthorized access to internal resources, potential data exfiltration, and system compromise. |
| Affected Products | Ivanti Connect Secure and Ivanti Policy Secure |
| Mitigation | Patch available; users urged to update immediately. |
| Patch Availability | Official patches released by Ivanti for affected versions. |
What is SSRF and Why It Is Bad
Server-Side Request Forgery (SSRF) allows an attacker to send requests from a vulnerable server to other systems, which the attacker might not directly access. This vulnerability can lead to unauthorized access to internal resources, data exfiltration, and potentially, full system compromise. SSRF vulnerabilities exploit the server’s capability to make requests to internal or external networks, thus bypassing network security measures like firewalls and access control lists. It is a dangerous exploit as it can enable attackers to query internal systems, potentially accessing sensitive data or exploiting internal services, emphasizing the need for vigilant security measures against such vulnerabilities.
Discovery and Analysis
The technical analysis provided by Rapid7 offers a deep dive into the vulnerability, starting with the identification of the auth bypass vulnerability (CVE-2023-46805). The investigation revealed that certain endpoints did not require authentication for access, notably including the SAML endpoint, which could be exploited through specially crafted unauthenticated HTTP POST requests. These requests would be dispatched to a back-end service responsible for SAML operations, potentially allowing attackers to manipulate SAML requests and responses.
Exploitation Technique
The exploitation of CVE-2024-21893 is particularly concerning due to its ability to bypass the original mitigations for the earlier vulnerabilities. By crafting a specific XML SOAP envelope containing a malicious RetrievalMethod element, attackers could trigger the SSRF vulnerability. This technique involves specifying an arbitrary URI in the URI attribute of the RetrievalMethod element, effectively allowing attackers to make the vulnerable server perform unintended HTTP requests to arbitrary locations.
Chaining Vulnerabilities for Remote Code Execution
What makes CVE-2024-21893 especially critical is its potential to be chained with CVE-2024-21887, enabling unauthenticated remote code execution. By leveraging the SSRF to make internal requests within the Ivanti appliance, attackers could exploit the command injection vulnerability, executing arbitrary commands on the system. This chain of vulnerabilities underscores the need for a comprehensive security approach that addresses both individual vulnerabilities and the potential for them to be exploited in concert.
Mitigation and Remediation
In response to the discovery of CVE-2024-21893 and its exploitation techniques, Ivanti has released a second mitigation file and official patches addressing the vulnerabilities involved in these exploit chains. It is imperative for organizations using Ivanti Connect Secure and Policy Secure appliances to apply these patches immediately to protect against potential attacks.
Collaboration
The joint efforts of cybersecurity experts, including those from Rapid7, are essential for detecting and addressing new security vulnerabilities. The identification and examination of CVE-2024-21893 underscore the need for ongoing alertness, prompt updates, and knowledge sharing in the cybersecurity field. Organizations that remain well-informed and proactive can significantly lower their vulnerability to complex security threats.
For Security Engineers: Protecting Against CVE-2024-21893 and CVE-2024-21888
Security engineers are on the front lines of implementing defenses against vulnerabilities like CVE-2024-21893 and CVE-2024-21888. Here’s what needs to be on their radar:
Patch Management
- Timely Patch Application: Ivanti has released patches for the affected versions. Ensuring these patches are applied promptly across all impacted systems is paramount.
- Patch Verification: After patch application, conduct thorough testing to ensure that the patches have been correctly applied and that they effectively mitigate the vulnerabilities without affecting system functionality.
Mitigation Strategies
- SSRF Mitigations: For CVE-2024-21893, ensure that all external entity interactions are securely configured to prevent unauthorized access. This may include strict URL filtering, and implementing proper input validation.
- Privilege Escalation Protections: To combat CVE-2024-21888, adhere to the principle of least privilege, ensuring users have only the permissions necessary for their role. Regular audits and monitoring for unusual activity can help detect attempts to exploit this vulnerability.
Detection and Alarms
- Monitoring and Logging: Implement comprehensive logging and monitoring strategies to detect potential exploitation attempts against these vulnerabilities. Early detection is crucial for a swift response.
- Education and Awareness: Keep your team informed about the latest vulnerabilities, patches, and mitigation techniques. A well-informed team is better equipped to prevent and respond to security threats.
Security teams, including SOC engineers and security analysts, should prioritize the monitoring of logs for signs of exploitation attempts against CVE-2024-21893. Here’s a structured approach to guide you in detecting suspicious activities:
Key Indicators to Monitor
HTTP POST Requests to SAML Endpoint: Be on alert for unexpected HTTP POST requests targeting the SAML service endpoint, specifically:
XML SOAP Envelope Patterns: Pay close attention to XML SOAP envelopes in requests. Anomalies such as unusual or out-of-place RetrievalMethod elements are red flags. Look for patterns like:
This pattern might indicate an attempt to exploit the SSRF vulnerability by directing the server to make unauthorized requests.
Conclusion
CVE-2024-21893 serves as a critical reminder of the ever-present and evolving nature of cybersecurity threats. The detailed analysis provided by Rapid7, alongside Ivanti’s responsive mitigation measures, exemplifies the importance of collaboration and proactive security practices in the face of sophisticated cyber-attacks. As we move forward, the lessons learned from the handling of CVE-2024-21893 will undoubtedly contribute to stronger, more resilient cybersecurity defenses.
References
For further reading and a deeper dive into the technical aspects of CVE-2024-21893, the following resources are invaluable:
- Rapid7 Analysis of CVE-2024-21893: AttackerKB Topic – Detailed analysis and insights from Rapid7.
- Ivanti Security Update: Ivanti Blog Post – Official security update for Ivanti Connect Secure and Ivanti Policy Secure Gateways.
- CVE-2024-21888 Privilege Escalation: Ivanti Forums – Discussion on privilege escalation vulnerability.
- Rapid7 Analysis of CVE-2023-46805: AttackerKB Topic – Insights into the CVE-2023-46805 vulnerability.
- Early Detection and Response: Rapid7 Blog Post – Early detection and response to the exploitation of Ivanti Connect Secure and Policy Secure Gateways.
- Third Ivanti Zero-Day Vulnerability CVE-2024-21893: eSentire Security Advisory – Advisory on the third Ivanti zero-day vulnerability.
These resources offer comprehensive insights and guidance on addressing the vulnerabilities, ensuring that security teams are equipped with the knowledge needed to protect their systems against these sophisticated threats.