The U.S. Cybersecurity and Infrastructure Security Agency (CISA) has recently issued an important advisory regarding two critical vulnerabilities found in Sitecore CMS. These vulnerabilities, identified as CVE-2019-9874 and CVE-2019-9875, have been officially added to CISA’s Known Exploited Vulnerabilities (KEV) catalog. This inclusion signals the active exploitation of these flaws in real-world scenarios and underscores the need for organizations using Sitecore to address and remediate the issues immediately.

In this comprehensive discussion, we will explore the details of these vulnerabilities, their potential impact, the mechanisms by which they can be exploited, and the steps organizations should take to protect themselves. The following sections offer an in-depth look at each aspect of the issue, providing a clearer understanding for security professionals and system administrators.

Background on CVE-2019-9874 Sitecore CMS Vulnerabilities

Sitecore is a widely used content management system (CMS) that powers many enterprise websites and digital experiences. Given its broad adoption, any vulnerability within Sitecore can have widespread implications. The two vulnerabilities in focus here, CVE-2019-9874 and CVE-2019-9875, affect the Sitecore.Security.AntiCSRF module—a component designed to protect against Cross-Site Request Forgery (CSRF) attacks. Unfortunately, flaws in this module have paved the way for potential remote code execution (RCE) attacks, a highly dangerous class of exploits that enable attackers to execute arbitrary code on affected systems.

CIA’s Role and the KEV Catalog

CISA plays a crucial role in identifying, cataloging, and advising on vulnerabilities that pose significant risks to critical infrastructure. The inclusion of these two Sitecore vulnerabilities in the KEV catalog is an alarming signal to organizations and government agencies alike. CISA’s action reinforces the message that despite patches and fixes being available, the vulnerabilities continue to be exploited actively. For federal agencies under the Federal Civilian Executive Branch (FCEB), there is a mandated deadline to apply available patches by April 16, 2025. This deadline highlights the urgency of addressing these issues promptly.

Detailed Examination of the Vulnerabilities

Understanding the nature and specifics of each vulnerability is essential to grasping the scope of the threat. The following sections detail the technical aspects and differences between the two vulnerabilities.

CVE-2019-9874: A Critical, Unauthenticated Threat

CVE-2019-9874 is considered a severe vulnerability primarily due to its classification, with a CVSS score of 9.8. This rating reflects the extreme risk it poses to organizations that have not secured their Sitecore installations. The vulnerability arises from a deserialization flaw within the Sitecore.Security.AntiCSRF module. Attackers who exploit this vulnerability do not need to authenticate themselves, which makes it an even more attractive target for cybercriminals.

The primary attack vector involves tampering with the __CSRFTOKEN parameter in an HTTP POST request. By injecting a maliciously crafted serialized .NET object into this parameter, an attacker can trigger remote code execution. This means that an attacker can run any code on the targeted server, bypassing normal security checks. In real-world terms, this vulnerability could allow unauthorized users to gain full control over a website, steal sensitive data, or use the compromised system as a launching pad for further attacks.

CVE-2019-9875: A High-Risk Vulnerability Requiring Authentication

While CVE-2019-9875 affects the same anti-CSRF module as CVE-2019-9874, it differs in that it requires the attacker to be authenticated before exploitation is possible. Despite this added layer of security, the vulnerability still carries a significant risk, as reflected by its CVSS score of 8.8. Once an attacker successfully authenticates, they can leverage a similar deserialization process to execute arbitrary code on the server.

In this case, the attacker’s capabilities extend beyond mere data breaches; they can hijack the server and conduct further malicious activities. Even though the need for authentication presents a higher barrier to entry, the ease with which the deserialization vector can be weaponized should not be underestimated. Attackers can exploit this vulnerability using readily available tools like ysoserial.net, which can encode payloads designed to execute PowerShell commands. These commands can establish remote shells or deploy malware, effectively enabling a wide range of harmful actions without triggering traditional security alarms.

The Impact of Remote Code Execution Vulnerabilities

Remote code execution vulnerabilities represent one of the most dangerous security threats because they allow attackers to take control of a system from a distance. The ability to execute arbitrary code on a vulnerable server means that the attacker can alter the system’s behavior, access sensitive information, and potentially disrupt entire networks.

In the context of Sitecore CMS, the impact is particularly severe due to the platform’s widespread use in hosting critical business applications and customer-facing websites. The exploitation of either CVE-2019-9874 or CVE-2019-9875 could lead to:

Complete server takeover, where attackers gain administrative privileges.
Unauthorized access to databases and other backend systems.
Deployment of additional malware can lead to a chain reaction of security breaches.
Disruption of services, potentially resulting in significant downtime and financial losses.

For organizations that rely on Sitecore for their digital operations, the exploitation of these vulnerabilities could not only lead to immediate operational impacts but also long-term reputational damage.

How Attackers Exploit Deserialization Vulnerabilities

A key factor in both of these vulnerabilities is the concept of deserialization. Deserialization is the process of converting data from a byte stream back into an object. While this is a routine operation in many software systems, it can become dangerous when the process is not properly secured.

In the case of CVE-2019-9874 and CVE-2019-9875, the deserialization occurs in a stage prior to the execution of the application’s logic. This early stage of deserialization provides an opportunity for attackers to bypass the security controls that would otherwise prevent unauthorized code execution. By crafting a malicious .NET object and embedding it within the __CSRFTOKEN parameter, an attacker can hijack the normal flow of the application.

Tools like ysoserial.net simplify the process for attackers by generating serialized objects that can trigger remote code execution. With such tools at their disposal, attackers can encode payloads that execute commands such as launching PowerShell scripts. Once a payload is executed, the compromised system might spawn a remote shell or download and execute additional malware, further compromising the system’s integrity.

Versions Affected and the Scope of the Issue

Understanding which versions of Sitecore are affected by these vulnerabilities is crucial for organizations planning their remediation efforts. The breakdown of affected products is as follows:

CVE-2019-9874 impacts Sitecore CMS versions 7.0 through 7.2, as well as Sitecore XP versions 7.5 through 8.2.
CVE-2019-9875 affects Sitecore versions up to 9.1.0.

This wide range of affected versions highlights that many organizations, especially those that have not upgraded their Sitecore installations in recent years, are at risk. The fact that these vulnerabilities were discovered in 2019 but continue to be exploited in 2025 emphasizes the persistence of security threats and the importance of regular software updates and patch management.

Mitigation Strategies and Remediation Measures

Given the active exploitation of these vulnerabilities, immediate action is necessary. Sitecore released patches and fixes shortly after the initial disclosure of these vulnerabilities in 2019. However, many organizations remain unpatched, which continues to expose them to risk. The following mitigation strategies should be considered by all organizations using Sitecore:

Applying the Official Patches

For organizations that have not yet applied the patches, the first step is to review the official advisories and apply the appropriate updates:

For Sitecore installations running versions prior to 9.0, a hotfix is available, as documented in Sitecore KB Article 334035.
For installations running Sitecore 9.0 and later, upgrading to Sitecore 9.1 Update-1 is necessary to resolve the issue.

Implementing these patches is critical to closing the security gap and preventing unauthorized code execution.

Temporary Workarounds

While organizations work on applying the official patches, temporary workarounds can help mitigate the risk:

One effective method is to restrict access to the \Website\sitecore\shell folder on all Sitecore instances. This can be done by configuring the server to deny external access to this directory, reducing the potential attack surface.
Additionally, implementing IP-based restrictions to limit access only to trusted addresses can provide a layer of defense until patches can be applied.

Incorporating Vulnerability Management Practices

CISA’s advisory emphasizes that organizations should use the KEV catalog as a guide to inform their vulnerability management prioritization frameworks. This means that in addition to addressing the Sitecore vulnerabilities, organizations should integrate this information into their broader security posture. This integration may involve:

Conducting regular vulnerability assessments to identify any other exposed systems.
Updating incident response plans to include scenarios involving remote code execution.
Training staff on recognizing signs of exploitation and ensuring rapid reporting and response.

Importance of Regular Software Updates

The recurrence of these vulnerabilities, which were first disclosed six years ago, serves as a reminder of the critical importance of keeping software up-to-date. Even when vulnerabilities are patched, the continued use of older, unpatched versions can leave organizations exposed to threats. Routine reviews of software deployments, coupled with prompt application of security updates, are essential best practices that help mitigate risks associated with legacy systems.

The Broader Implications for Cybersecurity

The active exploitation of these Sitecore vulnerabilities is not just a technical issue—it also reflects broader challenges in the cybersecurity landscape. Several key points emerge from this case:

The Enduring Challenge of Legacy Systems

Many organizations continue to run older versions of critical software due to compatibility issues, resource constraints, or a lack of awareness about emerging threats. The Sitecore vulnerabilities exemplify how legacy systems can remain attractive targets for attackers long after a vulnerability has been disclosed and even patched. This underscores the need for comprehensive asset management and proactive updating policies to ensure that all systems, regardless of age, are secured against known threats.

The Evolution of Attack Tools

The availability of tools like ysoserial.net highlights a concerning trend in the evolution of attack methodologies. These tools lower the barrier to entry for exploiting vulnerabilities by automating complex processes such as payload generation and deserialization attacks. As cybercriminals gain access to more sophisticated and user-friendly exploit tools, organizations must continuously update their defenses and ensure that their security infrastructure can detect and mitigate these advanced attack vectors.

Impact on Critical Infrastructure and Business Operations

For many enterprises, the compromise of a Sitecore-based system could have far-reaching consequences. Websites powered by Sitecore often serve as the primary interface for customer engagement and business operations. A successful remote code execution attack not only jeopardizes sensitive data but can also disrupt critical services, leading to financial losses and damage to the organization’s reputation. The cascading effects of such an attack can extend well beyond the initial breach, affecting supply chains, customer trust, and long-term business viability.

The Role of Regulatory and Government Agencies

The inclusion of these vulnerabilities in CISA’s KEV catalog and the subsequent mandate for federal agencies highlight the role of government and regulatory bodies in safeguarding critical infrastructure. By maintaining and updating catalogs of known vulnerabilities, agencies like CISA provide an essential service to the cybersecurity community, ensuring that organizations are informed about the latest threats and the best practices for addressing them. This collaborative approach between the public and private sectors is vital for building a resilient cybersecurity framework.

Steps for Security Professionals and Organizations

For security professionals and IT administrators, the situation presents an opportunity to re-evaluate current practices and implement measures that reduce the risk of exploitation. The following steps are recommended for those managing Sitecore deployments:

Immediate Patch Deployment: Review your current Sitecore version and determine if it falls within the affected range. Apply the hotfix for versions prior to 9.0 or upgrade to Sitecore 9.1 Update-1 as soon as possible.
Implement Temporary Controls: Until patches can be fully deployed, restrict access to vulnerable directories and apply IP-based access restrictions to limit exposure to known and trusted sources.
Conduct a Comprehensive Vulnerability Assessment: Use automated scanning tools to identify any instances of these vulnerabilities within your network. Regularly schedule such assessments to catch emerging threats early.
Review and Update Security Policies: Ensure that your organization’s incident response plan includes specific procedures for handling remote code execution attacks and other high-impact vulnerabilities.
Invest in Training and Awareness: Equip your team with the knowledge and tools needed to identify and respond to deserialization attacks. Training should cover the latest exploitation techniques and the importance of adhering to best practices in software security.
Monitor Cyber Threat Intelligence Feeds: Stay informed about the latest developments in cybersecurity by subscribing to threat intelligence feeds and updates from agencies like CISA. This proactive approach can help you anticipate and prepare for emerging threats.

Looking Ahead: The Future of Web Application Security

The active exploitation of vulnerabilities in widely used platforms like Sitecore is a reminder that web application security remains a moving target. As new vulnerabilities are discovered and exploitation techniques evolve, organizations must adopt a mindset of continuous improvement in their security practices. The following factors are expected to shape the future of web application security:

Increasing Sophistication of Attacks

Attackers are continually refining their methods, often leveraging automation and artificial intelligence to identify and exploit vulnerabilities more rapidly than ever before. As a result, organizations must invest in advanced threat detection and response systems that can analyze vast amounts of data in real-time and identify suspicious patterns before they lead to breaches.

Enhanced Collaboration Between Public and Private Sectors

The collaboration between government agencies, such as CISA, and private organizations is crucial in combating widespread vulnerabilities. By sharing threat intelligence, best practices, and remediation strategies, the cybersecurity community can collectively raise the bar on defense mechanisms. This joint effort is essential for mitigating risks that affect not just individual organizations but the entire digital ecosystem.

Greater Emphasis on Secure Software Development

The recurring nature of vulnerabilities like those found in Sitecore underscores the need for a shift towards more secure software development practices. Organizations are increasingly adopting DevSecOps—a philosophy that integrates security practices into every stage of the software development lifecycle. By building security into the design and testing phases, developers can reduce the likelihood of vulnerabilities in production environments.

Regulatory Pressure and Compliance

With cyberattacks becoming more prevalent and damaging, regulatory bodies are likely to impose stricter requirements on organizations to protect their digital assets. Compliance with standards such as the NIST Cybersecurity Framework, ISO 27001, and industry-specific regulations will become increasingly important. This regulatory pressure will drive organizations to prioritize timely updates, thorough vulnerability assessments, and robust incident response strategies.

Final Thoughts: Proactive Security as a Strategic Priority

The inclusion of CVE-2019-9874 and CVE-2019-9875 in CISA’s KEV catalog is a stark reminder that even vulnerabilities identified years ago can remain active and dangerous if not properly addressed. For organizations using Sitecore CMS, this is a critical wake-up call to reassess and fortify their security posture.

Addressing these vulnerabilities is not merely a matter of compliance; it is an essential step in protecting valuable assets, maintaining customer trust, and ensuring the continued smooth operation of digital services. The proactive measures discussed—from immediate patching to the adoption of advanced security frameworks—are vital components of a comprehensive strategy aimed at mitigating risk in an increasingly hostile digital environment.

In summary, the landscape of web application security is continuously evolving. By staying informed about the latest vulnerabilities, applying patches promptly, and implementing robust mitigation measures, organizations can significantly reduce the risk of exploitation. Security professionals must be in charge of integrating these practices into everyday operations, ensuring that digital infrastructures remain resilient in the face of emerging threats.

Ultimately, while the technical details of CVE-2019-9874 and CVE-2019-9875 may seem daunting, they provide an opportunity for organizations to strengthen their cybersecurity defenses and adopt a forward-looking approach to managing risk. The lessons learned from this case can serve as a roadmap for addressing future vulnerabilities and fortifying the digital landscape for years to come.

Reference: Cybersecurity News, CVE.org

CVE-2019-9874: Understanding the Sitecore CMS Vulnerabilities