Equifax is one of the largest credit reporting agencies in the world, alongside Experian and TransUnion. The company collects and maintains vast amounts of personal and financial data on hundreds of millions of consumers and businesses. This data is used for credit scoring, loan approvals, and identity verification, making Equifax a prime target for cybercriminals. The scale and sensitivity of the data handled by Equifax amplify the impact of any security incident, especially a breach of the magnitude seen in 2017.

• March 7, 2017: Apache Software Foundation discloses CVE-2017-5638 and releases a patch for the vulnerability in Apache Struts.
• March 10, 2017: Attackers begin exploiting the vulnerability in Equifax’s systems.
• May 13, 2017: Malicious activity continues undetected for over two months.
• July 29, 2017: Equifax discovers suspicious network traffic and begins investigation.
• September 7, 2017: Equifax publicly discloses the data breach.

The breach timeline underscores the critical importance of timely patch management and effective threat detection.

Apache Struts is an open-source web application framework used for building Java EE web applications. It is widely adopted by enterprises for developing scalable, maintainable, and flexible web applications. Struts provides a set of tools and libraries that simplify the development of complex web applications, but its popularity also makes it a frequent target for cyberattacks. For more details, see the official Apache Struts documentation.

The CVE-2017-5638 vulnerability is a critical remote code execution (RCE) flaw in the Apache Struts 2 framework. Specifically, it affects the Jakarta Multipart parser used for file uploads. The flaw allows an attacker to send a specially crafted Content-Type HTTP header, which the parser fails to properly validate, leading to arbitrary code execution on the target server.

According to the NIST National Vulnerability Database, the vulnerability received a CVSS score of 10.0, the highest possible severity rating. This made it a high-priority target for attackers and a critical patch for organizations using the affected versions of Struts.

Attackers exploited CVE-2017-5638 by sending HTTP requests with malicious Content-Type headers to Equifax’s web applications. The vulnerable Struts component failed to properly sanitize these headers, allowing attackers to inject and execute arbitrary commands on the server. Once inside, the attackers moved laterally, escalating privileges and exfiltrating sensitive data over several months.

The exploit process can be summarized as follows:

• Send a crafted HTTP request with a malicious Content-Type header.
• The vulnerable Struts parser executes attacker-supplied code.
• Attackers gain remote access to the affected server.
• Further compromise of internal systems and databases.
• Exfiltration of sensitive personal and financial data.

For a technical breakdown of the exploit, refer to OWASP’s analysis of Apache Struts RCE.

The Equifax Data Breach 2017 resulted in the exposure of highly sensitive information, including:

• Names
• Social Security Numbers
• Birth dates
• Addresses
• Driver’s license numbers
• Credit card numbers (for approximately 209,000 consumers)
• Dispute documents containing personal information

The scale and sensitivity of the compromised data made this breach particularly damaging, as it enabled identity theft and financial fraud on a massive scale.

For affected individuals, the breach posed significant risks, including:

• Increased likelihood of identity theft and fraud
• Potential for unauthorized credit activity
• Long-term exposure to phishing and social engineering attacks
• Emotional distress and loss of trust in credit reporting agencies

According to the Federal Trade Commission (FTC), consumers were urged to monitor their credit reports and consider credit freezes to mitigate the risk of identity theft.

The breach had severe consequences for Equifax, including:

• Loss of consumer trust and brand reputation damage
• Resignation of key executives, including the CEO, CIO, and CSO
• Regulatory investigations and lawsuits
• Financial losses, including a $700 million settlement with the FTC, CFPB, and states (FTC press release)
• Increased scrutiny of cybersecurity practices in the financial sector

The incident highlighted the far-reaching impact of cybersecurity failures on both organizations and the broader public.

Equifax discovered suspicious network activity on July 29, 2017, more than four months after the initial exploitation. The company launched an internal investigation and engaged cybersecurity experts to assess the breach’s scope. On September 7, 2017, Equifax publicly disclosed the incident, offering free credit monitoring and identity theft protection services to affected individuals.

The delay between detection and disclosure drew criticism from regulators and the public, highlighting the need for timely breach notification.

In response to the breach, Equifax implemented several remediation measures:

• Immediate patching of vulnerable systems
• Comprehensive security audits and penetration testing
• Enhanced network segmentation and monitoring
• Deployment of advanced threat detection tools
• Improved incident response protocols

Equifax also worked with federal and state regulators to strengthen its cybersecurity posture and prevent future incidents.

The breach triggered extensive regulatory and legal actions, including:

• Investigations by the Federal Trade Commission (FTC), Consumer Financial Protection Bureau (CFPB), and state attorneys general
• Multiple class-action lawsuits from affected consumers
• Congressional hearings on data security and consumer protection
• A $700 million settlement to resolve federal and state investigations (FTC settlement details)

These actions underscored the growing regulatory focus on data protection and the need for robust cybersecurity governance.

The Equifax breach highlighted the critical importance of timely patch management. Although a patch for CVE-2017-5638 was released on March 7, 2017, Equifax failed to apply it promptly, leaving systems exposed for months. Organizations must:

• Maintain an up-to-date inventory of software assets
• Monitor vulnerability disclosures from trusted sources such as CISA and NIST
• Implement automated patch management solutions
• Prioritize patching based on risk and severity

For best practices in vulnerability management, see the CIS Controls for Vulnerability Management.

Modern organizations rely heavily on third-party and open-source software. The Equifax incident demonstrates the risks associated with these dependencies. To mitigate such risks:

• Conduct regular security assessments of third-party components
• Monitor for updates and security advisories from software vendors
• Implement software composition analysis tools to detect vulnerable libraries
• Establish a process for rapid response to third-party vulnerabilities

Refer to OWASP Dependency-Check for tools and guidance on managing software supply chain risks.

An effective incident response plan is essential for minimizing the impact of security breaches. Equifax’s delayed detection and response allowed attackers to operate undetected for months. Key elements of a robust incident response program include:

• Clear roles and responsibilities for incident handling
• Regular incident response training and tabletop exercises
• Continuous monitoring and threat detection capabilities
• Timely communication with stakeholders and regulators

For comprehensive guidance, consult the NIST Computer Security Incident Handling Guide.

To prevent incidents like the Equifax Data Breach 2017, organizations should implement the following best practices:

• Patch Management: Apply security patches promptly and automate where possible.
• Asset Inventory: Maintain a comprehensive inventory of hardware and software assets.
• Vulnerability Scanning: Regularly scan systems for known vulnerabilities. For an in-depth comparison of modern tools, review the top network monitoring tools available in 2025.
• Network Segmentation: Limit lateral movement by segmenting critical systems.
• Least Privilege: Restrict user and system privileges to the minimum necessary.
• Security Awareness Training: Educate employees on phishing, social engineering, and secure coding practices.
• Incident Response Planning: Develop, test, and update incident response plans regularly. For practical steps, see how to build and test an incident response plan.
• Third-Party Risk Management: Assess and monitor the security posture of vendors and partners.

For a comprehensive checklist, refer to the CIS Critical Security Controls.

While organizations bear the primary responsibility for securing data, individuals can take steps to protect themselves in the aftermath of breaches:

• Monitor credit reports for suspicious activity
• Consider placing a credit freeze or fraud alert
• Use strong, unique passwords for online accounts—learn how to generate random passwords for improved security.
• Enable multi-factor authentication where available
• Be vigilant against phishing emails and scams
• Utilize identity theft protection services if offered

For more tips, visit the FTC Identity Theft Resource.

The Equifax Data Breach 2017 serves as a stark reminder of the devastating consequences of unpatched vulnerabilities and inadequate cybersecurity practices. The exploitation of the Apache Struts flaw (CVE-2017-5638) not only compromised the personal data of millions but also reshaped the regulatory landscape for data protection. By learning from this incident and implementing robust security measures, organizations and individuals can better defend against future threats and safeguard sensitive information. For organizations that want to ensure their defenses are up to par, conducting a professional password audit and recovery assessment is a critical preventative step.

• NIST National Vulnerability Database: CVE-2017-5638
• Apache Struts Official Documentation
• OWASP: Apache Struts Remote Code Execution
• FTC: Equifax to Pay $575 Million Settlement
• FTC: Equifax Data Breach – What to Do
• CIS Controls: Vulnerability Management
• OWASP Dependency-Check
• NIST Computer Security Incident Handling Guide
• CIS Critical Security Controls
• FTC Identity Theft Resource
• Password Cracking Guide 2025: 5 Latest Techniques