As security experts and IT administrators worldwide install the latest May security updates from Microsoft, a new wave of attacks targeting Windows platforms draws urgent attention to the persistent threats that cloud modern computing. Researchers have confirmed active exploitation of five high-severity vulnerabilities that span Windows 11, Windows Server 2022, and prior versions, underscoring both the resilience of threat actors and the challenges of patching a sprawling software ecosystem. Despite sustained investment in platform security, evidence shows attackers remain adept at unearthing pathways to penetrate systems—often exploiting legacy components many believed to be finally retired.
On this month’s Patch Tuesday, Microsoft disclosed that five vulnerabilities—CVE-2025-30400, CVE-2025-30397, CVE-2025-32709, CVE-2025-32701, and CVE-2025-32706—are being actively exploited. The threat level for all is officially classified as “high,” according to the Microsoft Security Update Guide and corroborated by independent research from threat analysts at Heise and The Record Media. These vulnerabilities collectively affect Windows client and server systems, with confirmed attacks observed both in enterprise and consumer environments.
The persistence of Internet Explorer in the Windows ecosystem is partly due to compatibility requirements in corporate environments, where line-of-business applications may depend on legacy web standards. Microsoft provided IE mode within Edge to serve these needs, but security professionals warn this feature offers a lingering attack surface. The German Federal Office for Information Security (BSI) and independent researchers have repeatedly urged organizations to phase out dependency on legacy browser technologies as quickly as possible.
The exposure of Microsoft Defender—a core component of Windows security, deployed by default on tens of millions of endpoints—is alarming. While Microsoft states that real-world attacks have not yet been observed at scale, previous incidents demonstrate how quickly attackers reverse-engineer security updates. Hot on their trail, cybercriminals scan for newly patched flaws, often launching campaigns within days—or hours—of patch release.
Excel also remains a recurring avenue for malicious code attacks. While this month’s patch addressed vulnerabilities that could allow malicious Excel files to compromise a user’s machine, security analysts urge organizations to combine patching with strict user awareness programs and advanced attachment scanning to stay ahead of emerging macro-based threats.
Cloud security experts at Wiz and Orca Security have highlighted the shifting threat landscape, emphasizing that as organizations migrate workloads to the cloud, attackers have responded in kind—retargeting exploit development toward service misconfigurations and privilege escalation flaws in hyperscale platforms. Cross-referencing vendor advisories with findings from the Cloud Security Alliance indicates that the pace and sophistication of Azure-targeted attacks is accelerating, particularly as “lift-and-shift” migrations result in complex, hybrid architectures with overlapping security models.
However, historical experience suggests that even after patching, attackers may probe environments for systems missed during updates. Patch management platforms and endpoint monitoring tools such as Windows Update for Business, Microsoft Endpoint Manager, or third-party solutions from vendors like ManageEngine and Ivanti are crucial to inventorying assets and verifying patch compliance.
Another positive trend is the company’s improved detection and disclosure of vulnerabilities affecting critical cloud infrastructure, reflecting the reality of today’s hybrid IT landscapes. Collaboration with cloud service customers in providing guidance on configuration and least-privilege access represents an industry best practice.
The true challenge—and opportunity—lies in building resilient systems that can withstand and quickly recover from compromise, recognizing that perfect prevention may be unattainable, but rapid detection and response are within reach. As the ghost of Internet Explorer continues to haunt Windows environments, the Windows community is called to exorcise outdated systems once and for all, embracing a new era of proactive, layered cybersecurity.
If you haven’t already initiated your post-Patchday review, now is the time—before attackers exploit those who wait.
Source: heise online Patchday: Attackers attack Windows via five vulnerabilities
The Patchday Offensive: What’s Under Attack?
On this month’s Patch Tuesday, Microsoft disclosed that five vulnerabilities—CVE-2025-30400, CVE-2025-30397, CVE-2025-32709, CVE-2025-32701, and CVE-2025-32706—are being actively exploited. The threat level for all is officially classified as “high,” according to the Microsoft Security Update Guide and corroborated by independent research from threat analysts at Heise and The Record Media. These vulnerabilities collectively affect Windows client and server systems, with confirmed attacks observed both in enterprise and consumer environments.Internet Explorer: The Persistent Ghost in the Machine
Of particular note is the continuing exposure of systems to attacks via Internet Explorer mode, even though official support for Internet Explorer ended in June 2022. Attackers exploit a workflow in Microsoft Edge that invokes Internet Explorer compatibility, exposing legacy rendering engines and security models no longer maintained by Microsoft. This is not merely a theoretical risk—real-world attack campaigns have been observed tricking users into clicking crafted links. When Edge switches into IE mode to render these pages, unpatched vulnerabilities are triggered, leading to malware implantation or system takeover.The persistence of Internet Explorer in the Windows ecosystem is partly due to compatibility requirements in corporate environments, where line-of-business applications may depend on legacy web standards. Microsoft provided IE mode within Edge to serve these needs, but security professionals warn this feature offers a lingering attack surface. The German Federal Office for Information Security (BSI) and independent researchers have repeatedly urged organizations to phase out dependency on legacy browser technologies as quickly as possible.
Verifying the Threat: Active Exploitation
Cross-referencing advisories from Microsoft with threat intelligence feeds confirms the in-the-wild exploitation of these CVEs. Public proof-of-concept exploits for some vulnerabilities surfaced on GitHub and exploit databases within 24 hours of patch release, elevating the risk profile for systems not swiftly updated.The Common Log File System Driver: An Attractive Target
Among the vulnerabilities under active attack is one in the Windows Common Log File System (CLFS) driver—a recurring focal point for attackers over the years. Successful exploitation grants attackers system-level privileges, making it a potent escalation pathway after initial access. The CLFS component is a complex subsystem responsible for data logging across Windows services, and its privileged code runs at a high integrity level. Despite multiple rounds of patching in past years, CLFS-related vulnerabilities have reappeared in attack toolkits and have been leveraged by ransomware and espionage actors alike.Further Known Threats: Defender, Visual Studio, and Excel
The danger does not stop with the five actively exploited bugs. Microsoft has flagged two more vulnerabilities as publicly known and at potential risk of imminent attack: CVE-2025-26685 in Microsoft Defender, rated “medium,” and CVE-2025-32702 in Visual Studio, rated “high.” In both cases, attackers can deliver malicious code, raising the likelihood of malware infections through either software supply chain manipulation or targeted phishing.The exposure of Microsoft Defender—a core component of Windows security, deployed by default on tens of millions of endpoints—is alarming. While Microsoft states that real-world attacks have not yet been observed at scale, previous incidents demonstrate how quickly attackers reverse-engineer security updates. Hot on their trail, cybercriminals scan for newly patched flaws, often launching campaigns within days—or hours—of patch release.
Excel also remains a recurring avenue for malicious code attacks. While this month’s patch addressed vulnerabilities that could allow malicious Excel files to compromise a user’s machine, security analysts urge organizations to combine patching with strict user awareness programs and advanced attachment scanning to stay ahead of emerging macro-based threats.
Azure in the Crosshairs: Cloud Security Comes Under Fire
Beyond on-premises risks, Microsoft’s own cloud platform Azure is implicated in two critical vulnerabilities this month—CVE-2025-29827 and CVE-2025-29972. Both allow remote attackers to gain enhanced user rights in certain Azure services, an especially worrisome prospect given the concentration of sensitive workloads on the platform. While Microsoft has moved swiftly to remediate these issues and provides clear mitigation guidance, organizations leveraging Azure are urged to prioritize cloud patch management and regularly audit administrative access.Cloud security experts at Wiz and Orca Security have highlighted the shifting threat landscape, emphasizing that as organizations migrate workloads to the cloud, attackers have responded in kind—retargeting exploit development toward service misconfigurations and privilege escalation flaws in hyperscale platforms. Cross-referencing vendor advisories with findings from the Cloud Security Alliance indicates that the pace and sophistication of Azure-targeted attacks is accelerating, particularly as “lift-and-shift” migrations result in complex, hybrid architectures with overlapping security models.
Anatomy of an Attack: From Lure to Breach
Recent attack chains associated with these vulnerabilities follow a well-rehearsed pattern:- Initial Access
- Victims are directed to malicious links, typically via phishing emails impersonating trusted contacts or business partners.
- Social engineering leverages urgency (“Your account needs verification!”) or curiosity (“You have received a new voicemail!”).
- Triggering the Vulnerability
- When users click on the link, Microsoft Edge opens in Internet Explorer compatibility mode due to embedded legacy code requirements from the link or the targeted web resource.
- A crafted exploit triggers the vulnerability, allowing remote code execution—often without user awareness.
- Payload Delivery and Privilege Escalation
- Malicious payloads are dropped, either in memory or on disk, often disguised as legitimate executables or utilities.
- The attacker seeks to escalate privileges—using exploits like the CLFS driver vulnerability—gaining persistence.
- Lateral Movement and Data Exfiltration
- Once inside, attackers scan for sensitive data or pivot to other systems, sometimes using Azure privilege escalation flaws to leap from compromised workstations to cloud resources.
How Organizations Can Defend Themselves
1. Patch Immediately—But Prepare for Residual Risk
The number one defense against exploitation of freshly disclosed vulnerabilities is rapid application of security updates. Microsoft’s Security Update Guide provides detailed, system-specific patching instructions. IT administrators are encouraged not only to patch endpoints and servers, but also to check network appliances, embedded systems, and cloud deployments for vulnerable components.However, historical experience suggests that even after patching, attackers may probe environments for systems missed during updates. Patch management platforms and endpoint monitoring tools such as Windows Update for Business, Microsoft Endpoint Manager, or third-party solutions from vendors like ManageEngine and Ivanti are crucial to inventorying assets and verifying patch compliance.
2. Minimize Exposure to Legacy Components
Organizations must accelerate efforts to eliminate or strictly limit the use of Internet Explorer and other legacy components. Microsoft’s Internet Explorer mode within Edge offers necessary compatibility for certain aging web applications, but IT teams should inventory and modernize or retire these dependencies whenever possible. Group Policy settings can explicitly restrict the use of IE mode, and web application modernization initiatives should be prioritized as part of digital transformation roadmaps.3. Harden Cloud and Enterprise Security Posture
For Azure customers and hybrid cloud tenants, several practical steps enhance security:- Regularly review and update Role-Based Access Control (RBAC) assignments.
- Apply Azure Security Center recommendations and enable automated threat detection.
- Implement Just-in-Time (JIT) VM access to reduce the window of vulnerability.
- Enforce Multi-Factor Authentication (MFA) for all privileged accounts.
4. Layered Defense Strategies
Security experts universally agree: defense-in-depth remains the best response to evolving threats. A multifaceted strategy combining the following is key:- Up-to-date, cloud-managed endpoint protection leveraging real-time behavioral analysis.
- Strict least-privilege access for all users and administrators.
- Network segmentation to limit lateral movement from end-user devices or exposed legacy components.
- Constant monitoring and rapid response to suspicious activity via Security Information and Event Management (SIEM) or Extended Detection and Response (XDR) platforms.
Critical Analysis: Strengths, Weaknesses, and Risk Outlook
Strengths in Microsoft’s Security Response
Microsoft’s transparency and speed in responding to in-the-wild exploits are notable. Publicly available patch details, threat analytics via Microsoft 365 Defender, and proactive notifications distributed to enterprise customers demonstrate a maturing security ecosystem. The company’s embrace of “continuous patching” aligns with recommendations from both industry and government partners.Another positive trend is the company’s improved detection and disclosure of vulnerabilities affecting critical cloud infrastructure, reflecting the reality of today’s hybrid IT landscapes. Collaboration with cloud service customers in providing guidance on configuration and least-privilege access represents an industry best practice.
Areas of Persistent Risk
Despite concerted efforts, several weaknesses remain:- Legacy Technical Debt: Internet Explorer, CLFS, and other legacy components persist in codebases and corporate environments. As long as backward compatibility trumps security, attackers will continue to find cracks in the armor.
- User Awareness Gaps: Phishing and social engineering remain highly effective, with many attacks succeeding not through technical brilliance, but through user distraction or fatigue.
- Patch Latency and Complexity: Large enterprises may face delays in applying patches due to internal testing, regulatory requirements, or the sheer scale of their infrastructure. Attackers often target these “long-tail” systems.
- Cloud Security Maturity: Organizations on the cloud adoption journey frequently lack necessary controls at the intersection of identity, access, and infrastructure configuration, allowing vulnerabilities to be compounded by misconfiguration.
The Ghost of Internet Explorer: A Cautionary Tale
The continued abuse of Internet Explorer mechanisms reminds the technology industry of the long lifecycle of legacy technology, even after “official” end-of-life. The need for backward compatibility is real, but so is the risk it carries. This lesson extends far beyond browsers: printers, drivers, Industrial Internet of Things (IIoT) devices, and proprietary middleware can all become attack vectors if not carefully managed and sunsetted.Recommendations for the Windows Community
For IT leaders, CISOs, and home users alike, several concrete actions emerge from the latest Patchday revelations:- Conduct an immediate inventory of all Windows and Windows Server instances; prioritize patching of systems with Internet Explorer mode enabled.
- Review the Security Update Guide for end-to-end coverage; don’t forget cloud workloads and third-party integrations.
- Educate all users—whether remote or on-premises—about the risks posed by phishing links and the signs of browser redirection attacks.
- For organizations with DevOps or software development pipelines, ensure Visual Studio and build server environments are updated and protected against high-severity flaws.
- Where applicable, develop and test incident response playbooks that address both on-premises incidents and escalations to cloud or hybrid environments.
Conclusion: Vigilance in a Hybrid World
The May Patchday serves as a stark reminder that today’s enterprise surface area is vast and deeply interconnected. Attackers are well-resourced and opportunistic, leaping on vulnerabilities the moment they are disclosed, adapting their techniques to legacy code and new cloud paradigms alike. For defenders, this demands not only technical agility but a cultural commitment to continuous improvement—a recognition that patching, user education, and architectural modernization are ongoing journeys, not destinations.The true challenge—and opportunity—lies in building resilient systems that can withstand and quickly recover from compromise, recognizing that perfect prevention may be unattainable, but rapid detection and response are within reach. As the ghost of Internet Explorer continues to haunt Windows environments, the Windows community is called to exorcise outdated systems once and for all, embracing a new era of proactive, layered cybersecurity.
If you haven’t already initiated your post-Patchday review, now is the time—before attackers exploit those who wait.
Source: heise online Patchday: Attackers attack Windows via five vulnerabilities
