June’s Patch Tuesday has become a pivotal moment for Windows system administrators, threat researchers, and IT professionals alike. Microsoft’s June 2025 security update underlines why: it delivers patches for a total of 67 vulnerabilities, including two actively exploited zero-days and eight flagged as critical remote code execution threats. As always with Microsoft’s cycle, the numbers tell only part of the story—the true significance lies in the nature, context, and historical backdrop of the vulnerabilities themselves.
One of the most impactful headlines this month centers on CVE-2025-33053: a zero-day vulnerability in the WebDAV (Web Distributed Authoring and Versioning) implementation across all supported Windows editions. WebDAV’s story traces back to the late 1990s, when it enabled collaborative document editing over HTTP and played a particularly key role in legacy Exchange Server deployments. Since then, its use and relevance have waned significantly, especially following Microsoft’s 2023 announcement that the associated WebClient service would no longer start by default.
That should have been the final curtain for WebDAV. However, as this zero-day proves, “deprecated” does not mean “safe from exploitation.” Microsoft continues to ship WebDAV support on its latest platforms—even Windows 11 24H2 and Windows Server 2025—maintaining a sizable attack surface for opportunistic and targeted attacks.
What makes CVE-2025-33053 especially notable is that it marks not only the first WebDAV zero-day in seven years, but also Microsoft’s first documented patch for a WebDAV exploit in that same period. The attack vector documented is relatively simple: exploitation requires a user to click on a malicious link, a technique that has persisted across generations of threat actors. The attack’s low complexity rating suggests that successful compromise requires minimal attacker expertise; the barrier to entry is lower than in some historical exploits.
Adam Barnett, Lead Software Engineer at Rapid7, offers a critical insight here: “It will surprise no one that Windows still more or less supports WebDAV, and that turns out to be a bit of a problem. Microsoft acknowledges Check Point Research (CPR) on the advisory; CPR in turn attributes exploitation of CVE-2025-33053 to an APT, which they track as Stealth Falcon, an established threat actor with a long-running interest in governments and government-adjacent entities across the Middle East and the surrounding area.” Stealth Falcon, a group notorious for its targeted attacks in geopolitically sensitive regions, immediately elevates the seriousness of the vulnerability.
Practical risk, of course, does come down to whether vulnerable components are running or even installed on a given endpoint. While Windows Server 2025 allows administrators to install the WebDAV Redirector server feature, thus enabling the WebClient service, a default installation won’t necessarily present an exploitable configuration. However, the general principle persists: deprecated, but still-supported components are low-hanging fruit for determined attackers.
Administrators must now weigh the risks of keeping legacy components available, even in so-called “hardened” installations. This episode also highlights the importance of defense-in-depth: network segmentation, endpoint detection, and robust user training remain essential tools, but timely patching stands paramount against opportunistic zero-days like this one.
There’s a degree of confusion, however, owing to inconsistent FAQs in Microsoft’s official advisory. Adam Barnett notes, “It’s not entirely clear…whether simply connecting is enough to trigger exploitation, or whether successful authentication is required, since there is currently conflicting language in two separate FAQ entries with almost-identical titles: ‘How could an attacker exploit this/the vulnerability?’” This ambiguity is more than academic; it influences every organization’s understanding of exposure and necessary countermeasures.
For CVE-2025-33073, the distinction between “connection” and “authentication” is critical. If merely connecting to a malicious server is sufficient for compromise, attackers could exploit drive-by scripts or social engineering vectors without requiring user credentials. In contrast, if authentication is necessary, the risk tilts toward targeted attacks against higher-value accounts with reusable (or more predictable) credentials.
As of now, the only prudent course is to assume the worst-case scenario: any connection to an untrusted SMB server may result in exploitation. This risk calculus points toward a conservative remediation strategy—including network hardening, disabling outbound SMB connections where practical, and accelerating patch deployment.
By targeting this linchpin of network authentication, attackers could leverage a successful exploit into sweeping privilege elevation or lateral movement throughout an organization’s infrastructure. Microsoft notes that exploitation is not trivial—the attacker must successfully “win a race condition”—but still considers widespread exploitation “more likely.” Importantly, the KDC proxy role is not enabled by default on most Windows Server domain controllers; it’s usually activated only in specialized network topologies.
For organizations that have KDC proxy enabled, Microsoft’s recommendation and the broader consensus among analysts is unequivocal: apply the patch immediately, and audit the role’s necessity and exposure within your environment.
Microsoft warns that exploitation is more likely than not, and the risk is compounded by the fact that patches for “Microsoft 365 Apps for Enterprise” (sometimes labelled as “Microsoft 365 for Office”) are not yet available. This leaves some of the most popular and widely deployed versions of Office exposed, at least for the interim.
The focus on Office Preview Pane as an attack vector is notable, because users and organizations alike may assume that they are protected by not “opening” suspicious documents in the classic sense. This highlights a perennial truth: the lines between viewing, previewing, and full execution are blurred, and determined attackers continuously probe for these gray areas.
Organizations should inventory Office installs, prioritize available patches, and consider risk mitigation strategies for unpatchable versions, such as disabling preview features, deploying advanced endpoint protection, and doubling down on user awareness campaigns.
Microsoft’s standard mitigation advice—stay current, enable automatic updates where feasible, and follow best practices in system administration—remains as pressing as ever. The cadence of patch releases, paired with the disclosure of actively exploited vulnerabilities, offers a sobering reminder: the patch window remains the prime opportunity for defenders to get ahead before threat actors operationalize new exploits.
Microsoft’s broad, if sometimes imperfect, approach to patching and disclosure is laudable, and the inclusion of all supported platforms for patches, even where the risk seems niche, speaks to an abundance of caution. However, the onus remains on organizations to review their configurations, ruthlessly audit legacy features, and keep all endpoints as current as possible.
For IT departments, system administrators, and security professionals navigating the treacherous waters of enterprise Windows infrastructure, the message is clear: the attack surface never truly shrinks—it only moves and evolves. Vigilance, adaptability, and a deep commitment to patch management are the best defenses against both real and potential threats. And as the June 2025 Patch Tuesday cycle so aptly demonstrates, the past is never truly past, especially when it comes to legacy code and the search for system stability in an unstable world.
Source: SecurityBrief New Zealand Microsoft tackles WebDAV zero-day in June 2025 patch update
A WebDAV Reckoning: The First Zero-Day in Seven Years
One of the most impactful headlines this month centers on CVE-2025-33053: a zero-day vulnerability in the WebDAV (Web Distributed Authoring and Versioning) implementation across all supported Windows editions. WebDAV’s story traces back to the late 1990s, when it enabled collaborative document editing over HTTP and played a particularly key role in legacy Exchange Server deployments. Since then, its use and relevance have waned significantly, especially following Microsoft’s 2023 announcement that the associated WebClient service would no longer start by default.That should have been the final curtain for WebDAV. However, as this zero-day proves, “deprecated” does not mean “safe from exploitation.” Microsoft continues to ship WebDAV support on its latest platforms—even Windows 11 24H2 and Windows Server 2025—maintaining a sizable attack surface for opportunistic and targeted attacks.
What makes CVE-2025-33053 especially notable is that it marks not only the first WebDAV zero-day in seven years, but also Microsoft’s first documented patch for a WebDAV exploit in that same period. The attack vector documented is relatively simple: exploitation requires a user to click on a malicious link, a technique that has persisted across generations of threat actors. The attack’s low complexity rating suggests that successful compromise requires minimal attacker expertise; the barrier to entry is lower than in some historical exploits.
Adam Barnett, Lead Software Engineer at Rapid7, offers a critical insight here: “It will surprise no one that Windows still more or less supports WebDAV, and that turns out to be a bit of a problem. Microsoft acknowledges Check Point Research (CPR) on the advisory; CPR in turn attributes exploitation of CVE-2025-33053 to an APT, which they track as Stealth Falcon, an established threat actor with a long-running interest in governments and government-adjacent entities across the Middle East and the surrounding area.” Stealth Falcon, a group notorious for its targeted attacks in geopolitically sensitive regions, immediately elevates the seriousness of the vulnerability.
Analysis: Legacy Services and The Art of Risk Management
The persistence of WebDAV support in Windows is both a strength and a weakness. On one hand, it provides backward compatibility and ensures continued support for niche or legacy workflows—attributes which large enterprise environments still, in some cases, depend on. On the other hand, the continued presence of the service, even in a “disabled by default” state, makes every supported Windows device a potential target for exploitation. The broad rollout of the CVE-2025-33053 patch—covering every supported Windows build—signals that Microsoft is acutely aware of the risk.Practical risk, of course, does come down to whether vulnerable components are running or even installed on a given endpoint. While Windows Server 2025 allows administrators to install the WebDAV Redirector server feature, thus enabling the WebClient service, a default installation won’t necessarily present an exploitable configuration. However, the general principle persists: deprecated, but still-supported components are low-hanging fruit for determined attackers.
Potential Risks and Real-World Impacts
Although exploitation requires user interaction, history teaches us that well-crafted spear-phishing campaigns can reliably drive a handful of clicks—especially among users in targeted organizations. Considering that Stealth Falcon is attributed to exploitation attempts, it is not far-fetched to imagine attacks directed at governmental, defense, or diplomatic networks in the Middle East and neighboring regions.Administrators must now weigh the risks of keeping legacy components available, even in so-called “hardened” installations. This episode also highlights the importance of defense-in-depth: network segmentation, endpoint detection, and robust user training remain essential tools, but timely patching stands paramount against opportunistic zero-days like this one.
The SMB Client Zero-Day: Ambiguities in Exploitation
The second zero-day, CVE-2025-33073, involves a classic avenue for privilege escalation: the Windows SMB (Server Message Block) client. This elevation-of-privilege (EoP) flaw, publicly disclosed ahead of the patch, is rated as more severe than it may initially appear. According to Microsoft, exploitation could allow an attacker to obtain SYSTEM-level privileges if a user connects to a maliciously crafted SMB share hosted by the attacker.There’s a degree of confusion, however, owing to inconsistent FAQs in Microsoft’s official advisory. Adam Barnett notes, “It’s not entirely clear…whether simply connecting is enough to trigger exploitation, or whether successful authentication is required, since there is currently conflicting language in two separate FAQ entries with almost-identical titles: ‘How could an attacker exploit this/the vulnerability?’” This ambiguity is more than academic; it influences every organization’s understanding of exposure and necessary countermeasures.
Analysis: A Legacy Protocol, Modern Threats
SMB remains deeply entrenched in enterprise Windows environments—used for file sharing, print services, and a range of IT administrative tasks. Its prominence has made it a frequent target in past ransomware events and cyber-espionage campaigns. Previous SMB vulnerabilities, such as the one exploited by WannaCry (CVE-2017-0144), have shown the devastating potential of flaws in this protocol.For CVE-2025-33073, the distinction between “connection” and “authentication” is critical. If merely connecting to a malicious server is sufficient for compromise, attackers could exploit drive-by scripts or social engineering vectors without requiring user credentials. In contrast, if authentication is necessary, the risk tilts toward targeted attacks against higher-value accounts with reusable (or more predictable) credentials.
As of now, the only prudent course is to assume the worst-case scenario: any connection to an untrusted SMB server may result in exploitation. This risk calculus points toward a conservative remediation strategy—including network hardening, disabling outbound SMB connections where practical, and accelerating patch deployment.
Windows KDC Proxy: Exposing the Heart of Authentication
Of the eight critical remote code execution vulnerabilities, CVE-2025-33071 deserves particular attention. Affecting the Windows KDC (Key Distribution Center) Proxy Service, this flaw could allow unauthenticated remote code execution due to a cryptographic protocol weakness. KDC proxies serve a specialized function: they bridge Kerberos authentication requests from less-trusted to more-trusted network domains, often sitting at the boundary between corporate networks and external environments.By targeting this linchpin of network authentication, attackers could leverage a successful exploit into sweeping privilege elevation or lateral movement throughout an organization’s infrastructure. Microsoft notes that exploitation is not trivial—the attacker must successfully “win a race condition”—but still considers widespread exploitation “more likely.” Importantly, the KDC proxy role is not enabled by default on most Windows Server domain controllers; it’s usually activated only in specialized network topologies.
Analysis: When “Not Default” Doesn’t Mean “Not Dangerous”
The distinction that a vulnerable service is not enabled by default is cold comfort in the world of modern threat hunting. History shows that sophisticated attackers actively scan for, identify, and exploit rarer configurations, precisely because organizations often underestimate their risk exposure. Furthermore, services that bridge trust boundaries—in this case, mediating Kerberos authentication—magnify the potential reward for an attacker willing to invest the effort.For organizations that have KDC proxy enabled, Microsoft’s recommendation and the broader consensus among analysts is unequivocal: apply the patch immediately, and audit the role’s necessity and exposure within your environment.
Office Preview Pane: A Persistent Avenue for Code Execution
Apart from platform-integrated services, the June 2025 cycle also addresses software that impacts vast numbers of knowledge workers: the Office suite. Microsoft patched three critical remote code execution vulnerabilities—CVE-2025-47162, CVE-2025-47164, and CVE-2025-47167—each discovered by the same researcher, and each exploitable via the Office Preview Pane. This vector is especially concerning, as users may not even open a malicious document—simply previewing it in Outlook or Explorer could trigger the exploit.Microsoft warns that exploitation is more likely than not, and the risk is compounded by the fact that patches for “Microsoft 365 Apps for Enterprise” (sometimes labelled as “Microsoft 365 for Office”) are not yet available. This leaves some of the most popular and widely deployed versions of Office exposed, at least for the interim.
Analysis: The Continuing Risk of Office-Based Attacks
Office-based code execution vulnerabilities have been staples of cybercriminal and espionage toolkits for decades. The reason is simple: Office documents remain among the most trusted and frequently exchanged file types in professional settings, and previewing files is a routine action.The focus on Office Preview Pane as an attack vector is notable, because users and organizations alike may assume that they are protected by not “opening” suspicious documents in the classic sense. This highlights a perennial truth: the lines between viewing, previewing, and full execution are blurred, and determined attackers continuously probe for these gray areas.
Organizations should inventory Office installs, prioritize available patches, and consider risk mitigation strategies for unpatchable versions, such as disabling preview features, deploying advanced endpoint protection, and doubling down on user awareness campaigns.
Broader Patch Landscape: Eight Critical RCEs and Lifecycle Rhythms
While the two zero-days and select remote code execution vulnerabilities command the spotlight, Microsoft’s June 2025 update covers a broader spectrum. Eight vulnerabilities are classified as “critical remote code execution,” with varying degrees of exploitability. These touch everything from core Windows components to specialized server roles and developer libraries.Critical RCEs: A Quick Table Reference
| CVE | Component | Description/Concern | Exploitation Likelihood |
|---|---|---|---|
| CVE-2025-33071 | Windows KDC Proxy | Unauthenticated RCE, cryptographic flaw | More likely |
| CVE-2025-47162 | Office Preview Pane | Preview triggers RCE, patch not yet for 365 Enterprise | More likely |
| CVE-2025-47164 | Office Preview Pane | See above | More likely |
| CVE-2025-47167 | Office Preview Pane | See above | More likely |
| … | (Other criticals) | Details in Microsoft advisory | Varies |
Product Lifecycle: No Drastic Changes, But Future Planning Needed
This June saw no major shake-ups in Microsoft’s product lifecycle. However, IT professionals should note upcoming deadlines: July will see the end of Extended Security Updates for SQL Server 2012, as well as support deadlines for Visual Studio 2022 17.8 LTSC. Staying informed about these transitions is just as vital as patching, since unsupported software quickly becomes a favorite playground for attackers.The Bigger Picture: Lessons from June 2025
Microsoft’s handling of this month’s vulnerabilities paints a picture of an ecosystem in continuous battle against both legacy complexity and modern adversaries’ ingenuity. Some takeaways, while perennial, are worth reiterating:1. Legacy Support Is a Double-Edged Sword
- Backward compatibility ensures broad software viability but multiplies risk over time. Deprecated services—even if not started by default—can still be targets for sophisticated threat actors.
2. Zero-Days Remain a Leading Threat
- Two zero-days, spanning both legacy (WebDAV) and modern (SMB) functionality, again prove that attackers invest in a spectrum of approaches—from phishing and social engineering to direct exploitation of network protocols.
3. Clarity (or Lack Thereof) in Advisories Can Hamper Response
- Ambiguity about exploitation conditions (as with the SMB client vulnerability) places the onus on defenders to err on the side of caution, sometimes at great operational cost.
4. Office Remains a Universal Attack Surface
- The continuing discovery of code execution flaws in Office exemplifies the need for both technical and human-centric defense layers. There is no substitute for rapid patching, but mitigating controls and security awareness can buy valuable time.
5. Patching Is Non-Negotiable, but Not Sufficient on Its Own
- Rapid deployment of patches is table stakes, not a panacea. Threat detection, lateral movement monitoring, incident response preparedness, and proactive configuration review all play critical roles.
Final Thoughts: Security Is an Ongoing Process
The June 2025 Patch Tuesday cycle is a microcosm of the broader struggle to keep complex, feature-rich, and long-lived software platforms secure in a world where both old and new exploits remain relevant. From WebDAV to SMB, legacy protocol support continues to create openings for determined adversaries. Meanwhile, the most widely used enterprise software tools, like Office, offer reliable—and lucrative—gateways for exploit development.Microsoft’s broad, if sometimes imperfect, approach to patching and disclosure is laudable, and the inclusion of all supported platforms for patches, even where the risk seems niche, speaks to an abundance of caution. However, the onus remains on organizations to review their configurations, ruthlessly audit legacy features, and keep all endpoints as current as possible.
For IT departments, system administrators, and security professionals navigating the treacherous waters of enterprise Windows infrastructure, the message is clear: the attack surface never truly shrinks—it only moves and evolves. Vigilance, adaptability, and a deep commitment to patch management are the best defenses against both real and potential threats. And as the June 2025 Patch Tuesday cycle so aptly demonstrates, the past is never truly past, especially when it comes to legacy code and the search for system stability in an unstable world.
Source: SecurityBrief New Zealand Microsoft tackles WebDAV zero-day in June 2025 patch update
