Commvault Metallic Cloud Backup Breach Highlights SaaS Security Risks & Best Practices

As the cybersecurity landscape continues to evolve, organizations increasingly rely on software-as-a-service (SaaS) solutions for essential operations such as cloud-based data backup and disaster recovery. However, with this shift comes new and complex threats—highlighted by the US Cybersecurity and Infrastructure Security Agency’s (CISA) recent advisory on targeted attacks exploiting Commvault’s cloud backup platform, Metallic, hosted on Microsoft Azure. The incident underscores persistent risks associated with SaaS solutions, particularly those managing vital authentication credentials for downstream applications like Microsoft 365 (M365). This detailed analysis examines the circumstances surrounding the attacks, the technical and operational lessons for IT administrators, and actionable recommendations to strengthen cloud security posture.

The Anatomy of the Attack: Commvault’s Metallic Under Fire​

In early March, Commvault—an established player in backup and recovery solutions—disclosed a security incident involving its Metallic SaaS environment. The breach first came to light after Microsoft identified unauthorized access within Commvault’s Azure-hosted infrastructure, likely perpetrated by a sophisticated, nation-state-affiliated attacker. According to both the company’s advisories and CISA’s public warning, the core vector centered on threat actors targeting the authentication credentials stored within Commvault’s cloud-based platform, specifically those used to integrate with customers’ Microsoft 365 environments.

Exploiting a Zero-Day: The Critical CVE-2025-3928 Vulnerability​

At the heart of the breach was the exploitation of a critical, previously unknown (zero-day) webserver vulnerability, now catalogued as CVE-2025-3928. Commvault’s investigation revealed that this vulnerability allowed attackers to bypass controls, accessing secrets tied to customer M365 accounts managed through Metallic on Azure. The attackers then leveraged these credentials to pivot into actual customer cloud environments—gaining the ability to access, or attempt to access, Microsoft 365 accounts.
While Commvault stated categorically that there was no evidence of unauthorized access to actual backup data or any material impact on core business operations, the incident presents vital lessons on the secondary and tertiary risks of SaaS solution compromise. The most concerning finding was not only the attackers’ ability to breach the Commvault environment, but their subsequent focus on sensitive cross-integrations—in this case, Microsoft 365 credentials—demonstrating how managed SaaS solutions can become a bridge to even more valuable enterprise assets.

A Broader Campaign Targeting Cloud Ecosystems​

CISA’s advisory situates the Commvault incident as likely being part of a broader, coordinated campaign. The common denominator: exploitation of default or overly permissive settings and misconfigurations across cloud applications and SaaS platforms. Given the prevalence of “unmanaged” SaaS apps on enterprise networks—estimated at 90% according to several industry reports—this campaign concept resonates deeply. Attackers do not need to breach every organization individually; compromising a SaaS provider or leveraging common configuration oversights can yield access to hundreds or thousands of downstream targets.

Incident Timeline and Communication​

Transparency and communication are vital benchmarks in incident response, especially when customer trust is on the line. Commvault’s handling of public disclosure is worth critical evaluation:

• Early March: Microsoft alerts Commvault of suspicious activity within the company’s Azure environment; Commvault launches a full investigation.
• March Advisory: Commvault informs customers and partners about unauthorized access, focusing on the limited scope of identified affected accounts and stressing the absence of breached backup data.
• April Update: Commvault shares emerging threat intelligence, acknowledging that a nation-state actor accessed M365 environments of a “small number” of joint Commvault-Microsoft customers. Enhanced technical measures and key rotation are rolled out, while indicators of compromise (IOCs) are shared for customer monitoring.
• May Update: The company reiterates findings, describes attack methods as “sophisticated” and aligns new optional security configurations with Microsoft’s recommended best practices. Commvault stresses that, as of that update, there is still no evidence of any customer backup data compromise.

It is crucial to note that both CISA and Commvault emphasize that attackers have not been conclusively identified, and no definitive attribution to a nation-state or specific threat group has been independently made by Commvault beyond signals from Microsoft.

Technical Lessons: Attack Surface in the SaaS Era​

SaaS Credential Chains and the M365 Risk​

A central risk illuminated by this incident is the chaining of credentials and permissions in modern SaaS ecosystems. When an organization uses a service like Commvault Metallic to safeguard its Microsoft 365 data, that service must necessarily be entrusted with privileged credentials to perform backup operations. Breaching the SaaS provider or exploiting misconfigurations can expose these credentials, enabling attackers to escalate privileges or move laterally—from the backup service to the productivity environment, and possibly further.
This threat multiplies in any environment where cloud applications and SaaS platforms are deeply interconnected, particularly when they are assigned broad, persistent permissions and secrets that are not routinely rotated, audited, or restricted in scope.

The Role of Default and Overly Permissive Configurations​

Both the original CISA advisory and Commvault’s updates highlight the systemic danger of default or overly-permissive access settings. Cloud applications often come with “out-of-the-box” privileges that facilitate ease of deployment but pose critical security risks. Attackers routinely scan for known defaults and lax policies—including global admin permissions, insufficiently scoped application secrets, and unmonitored API integrations—as soft entry points into more lucrative data stores.
On-premises deployments are not immune—CISA separately advised customers running Commvault’s on-premises backup software to restrict access to management interfaces, block path traversal exploits, and filter file uploads for malicious input, underscoring that the risk spans cloud and physical infrastructure alike.

Defensive Measures: Recommendations for SaaS and Cloud Providers​

To counter these advanced threat patterns, both CISA and Commvault outlined concrete, actionable steps, which every organization using cloud backup or other SaaS integrations should consider. Some of the most crucial include:

For SaaS Customers (e.g., Commvault Metallic Users):​

• Rotate All Application Secrets and Credentials: Routinely regenerate and replace credentials used for integrations, particularly those granting access to Microsoft 365 environments. This limits the window of opportunity for attackers armed with stolen secrets.
• Monitor Microsoft Entra (Azure AD) Audit Logs: Regularly review audit logs for any unauthorized changes, new application registrations, or credential modifications. Deviations from established login patterns should be treated as potential compromise signals, not mere anomalies.
• Apply Conditional Access Policies: Where possible, enforce conditional access for all single-tenant apps—limiting app access by location, device health, or even time of day.
• Revalidate Entra ID Permissions and Registrations: Systematically audit all registered apps, ensuring they have the minimum necessary permissions. Remove any stale, redundant, or broadly scoped app integrations.
• Enforce the Principle of Least Privilege: Ensure that app and user credentials only have the level of access strictly required for their function. Over-privileging remains a leading cause of lateral movement in cloud attacks.

For On-Premises Backup and SaaS Administrators:​

• Restrict Access to Management Interfaces: Where feasible, firewall off or otherwise restrict access to appliance or administrative interfaces. This reduces the risk of direct exploitation via network exposure.
• Block Path Traversal and Arbitrary File Uploads: Employ robust input validation and web application firewall (WAF) policies to detect and prevent attempts to upload unauthorized files or leverage path traversal exploits in management consoles.

Provider-Level (Commvault and SaaS Vendors):​

• Proactive Patch Management: Rapidly identify and patch newly discovered vulnerabilities, such as CVE-2025-3928 in this case. Timely patch rollouts—and clear customer notification—are critical.
• Incident Response and Transparency: Share detailed indicators of compromise (IOCs), attack patterns, and risk mitigation steps as soon as possible. Transparency builds trust and empowers customers to take informed action.
• Alignment with Major Cloud Provider Security Recommendations: Volt new configuration options and harden default settings in line with recommendations from Microsoft, AWS, Google Cloud, etc.

Emerging Trends: The Unmanaged SaaS Dilemma​

The Commvault incident is illustrative of a deeper, structural challenge facing modern enterprises: the explosion of “unmanaged” SaaS applications—cloud-connected tools not centrally provisioned or monitored by IT/security teams. Industry studies and CISA highlight a startling statistic: up to 90% of SaaS applications in large organizations are unmanaged, constituting massive blind spots for traditional security controls.
This unmanaged sprawl allows attackers to target weak links in the chain—such as outdated, under-secured integrations—that bypass conventional perimeter defenses. Complicating the picture is the evolving sophistication of threat actors, including advanced persistent threat groups capable of chaining vulnerabilities, abusing legitimate cloud features, and camouflaging movements within legitimate data flows.
On a more optimistic note, organizational awareness is on the rise. Recent industry surveys referenced by CISA suggest that up to 70% of enterprises have established, or are actively establishing, dedicated teams to mitigate SaaS-related security risk. Yet, bridging the gap between awareness and robust, enforceable policy remains a formidable challenge—as the Commvault breach demonstrates all too plainly.

Critical Strengths: What Commvault and the Ecosystem Got Right​

Despite the unsettling nature of a SaaS platform compromise, several positive elements deserve recognition in the response and ecosystem handling:

• Prompt Third-Party Notification: Microsoft’s rapid detection and escalation to Commvault exemplifies strong inter-vendor incident response, acting as an early warning that mitigated further compromise.
• Transparent Customer Communication: Repeated advisories—March, April, and May—ensured that stakeholders received up-to-date intelligence, ongoing technical guidance, and clear statements about the (limited) extent of impact.
• Proactive Patch Rollout and Key Rotation: Commvault’s ability to rapidly patch the CVE-2025-3928 zero-day and implement enhanced key rotation demonstrates operational maturity.
• Industry-Wide Awareness via CISA: CISA’s public advisories extend the learning opportunity to a much broader audience, ensuring that lessons from the incident contribute to better practices sector-wide.

Risks Exposed: Systemic Vulnerabilities and Industry Gaps​

While the breach was seemingly limited in scope, several clear risks are illuminated for both customers and providers:

• Credential Scope and Lifespan: Excessively broad, long-lived credentials stored within SaaS platforms constitute highly prized targets for attackers seeking access to multiple enterprise assets.
• Zero-Day Exposure: Attackers exploiting undisclosed (zero-day) vulnerabilities can bypass even well-maintained security controls. Early detection and rapid response are critical, but not always feasible.
• SaaS Supply Chain Risk: Organizations increasingly depend on multi-tiered SaaS supply chains (e.g., Azure, Commvault, M365), introducing complex, interdependent risk. A single breach at one node (such as Commvault) can have cascading amplification if permissions and integrations are insufficiently controlled.
• Attribution Ambiguity: Despite references to “nation-state” activity, Commvault stopped short of independent attribution—underscoring the challenges in conclusively identifying (and thus preempting) sophisticated adversaries in cloud environments.
• Visibility and Control Gaps: The overwhelming prevalence of unmanaged SaaS applications underscores pervasive gaps in enterprise visibility, monitoring, and control—challenges that cannot be addressed solely through technical quick fixes.

Making SaaS Work for Enterprise: Best Practices for 2025 and Beyond​

Drawing on lessons from the Commvault Metallic incident, organizations can and must shift their posture from reactive to proactive when it comes to SaaS security. A multipronged strategy is essential:

1. Centralize Visibility and Access Management​

Enterprises need unified oversight over all SaaS integrations—managed and unmanaged. Deploying cloud access security brokers (CASBs), SaaS security posture management (SSPM) tools, and robust identity and access management (IAM) solutions can help surface shadow IT and enforce policy at scale.

2. Automate Credential Rotation and Audit​

Manual credential management is no longer sufficient. Leveraging automated secret rotation, periodic credential audits, and stringent scoping is vital to limiting blast radius when credentials leak.

3. Fortify Integration Approval Processes​

Adopt a rigorous process for vetting and approving all third-party SaaS integrations. Enforce the use of least privilege and explicit permission granularity in all API and service principal configurations.

4. Enhance Endpoint and Behavioral Monitoring​

A focus on endpoints alone is inadequate; monitoring must extend to the cloud layer, encompassing SaaS activity logs, anomalous behavior detections, and cross-platform correlation. Routine review of Entra (Azure AD) and other cloud-native audit logs is a must.

5. Educate and Empower Staff​

Last, fostering a “security-first” culture—from developers through to end users—is essential. Training on SaaS risks, incident reporting, and secure practices can actively reduce the risk of inadvertent exposure or unintentional misconfigurations.

Conclusion: The Evolving SaaS-Cloud Security Paradigm​

The attack against Commvault’s Metallic environment serves as a timely and compelling case study in the risks and realities of modern cloud and SaaS environments. It validates that no solution is invulnerable—especially as attackers continue to innovate, discovering new ways to chain vulnerabilities, harvest over-broad credentials, and exploit trust relationships between SaaS platforms and their customers.
Yet, the incident also highlights positive trends: improved collaboration between major vendors, steadfast communication with stakeholders, and a groundswell of enterprise effort to reinforce SaaS security posture. As enterprises advance deeper into the world of interconnected cloud services, these dual lessons—vigilance and agility in defense, transparency and speed in incident response—will remain non-negotiable.
Ultimately, for every organization operating in today’s cloud-first universe, the simple act of entrusting a SaaS provider with core credentials demands a renewed focus on oversight, control, and partnership. Robust patching, vigilant log monitoring, least-privilege principles, and rigorous credential management emerge as the new minimum standards—backed by ongoing collaboration with SaaS vendors and global security agencies like CISA. In the era of infinite cloud connectivity, these fundamentals are not just best practices—they are business imperatives.

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Source: Dark Reading https://www.darkreading.com/cloud-security/cisa-warns-attacks-commvault-saas-environment/