Unmasking Stealth Falcon: Exploiting Windows WebDAV Zero-Day Vulnerability

The Stealth Falcon group has recently exploited a critical vulnerability in Microsoft’s Web Distributed Authoring and Versioning (WebDAV) service, known as CVE-2025-33053. This zero-day vulnerability allows remote code execution due to improper handling of file names or paths, posing a significant threat to systems worldwide. With a CVSS score of 8.8, the flaw is highly severe, impacting confidentiality, integrity, and availability (NVD). Stealth Falcon’s exploitation method involves a sophisticated attack chain that leverages legitimate Windows tools to execute malicious commands from a WebDAV server they control (Bleeping Computer). This attack highlights the evolving tactics of cyber espionage groups and underscores the importance of robust cybersecurity measures.

Exploitation of Windows WebDav Zero-Day Vulnerability by Stealth Falcon

Overview of CVE-2025-33053

CVE-2025-33053 is a critical remote code execution (RCE) vulnerability in Microsoft’s Web Distributed Authoring and Versioning (WebDAV) service. Imagine it as a secret backdoor left ajar, allowing unauthorized attackers to sneak in and execute arbitrary code over a network. The flaw has a CVSS Version 3.1 Base Score of 8.8, indicating a high severity level. The attack vector is network-based, requiring low attack complexity, no privileges, and user interaction, with a high impact on confidentiality, integrity, and availability (NVD).

Exploitation Technique

The Stealth Falcon group exploited this vulnerability using a sophisticated technique that involves manipulating the working directory of legitimate Windows tools. Picture a magician using sleight of hand to redirect attention; similarly, the attack begins with a specially crafted .url file, which points to iediagcmd.exe, a legitimate Internet Explorer diagnostics tool. This tool, when executed, performs various network diagnostic commands. However, due to the vulnerability, the tool is tricked into executing commands from a malicious WebDAV server controlled by the attackers (Bleeping Computer).

Attack Chain and Payload Delivery

The exploitation process involves setting the working directory to the attacker’s WebDAV server, causing iediagcmd.exe to execute a fake route.exe program from the remote server. This program installs a custom multi-stage loader known as ‘Horus Loader.’ The loader subsequently drops the primary payload, ‘Horus Agent,’ a custom C++ Mythic C2 implant. This implant supports various malicious activities, including command execution for system fingerprinting, configuration changes, shellcode injection, and file operations (Bleeping Computer).

Post-Exploitation Tools

After the initial compromise, Stealth Falcon employs several post-exploitation tools to maintain persistence and gather intelligence. These tools include a credential file dumper, a keylogger, and a passive backdoor that listens for encrypted shellcode payloads over the network. The use of these tools highlights the group’s focus on espionage and data exfiltration (Bleeping Computer).

Mitigation and Recommendations

Given the active exploitation of CVE-2025-33053, it is crucial for organizations, especially those in critical sectors, to apply the latest Windows updates promptly. If upgrading is not feasible, organizations should block or closely monitor WebDAV traffic for suspicious outbound connections to unknown endpoints. Additionally, implementing network segmentation and employing intrusion detection systems can help mitigate the risk of exploitation (Bleeping Computer).

Broader Implications and Threat Landscape

The exploitation of CVE-2025-33053 by Stealth Falcon underscores the evolving nature of cyber threats, particularly in the realm of cyber espionage. The group’s use of living-off-the-land binaries (LOLBins), multi-stage loaders, and a mix of native and .NET components demonstrates a creative approach to infection chains. This sophistication allows the attackers to blend in with legitimate system operations, making detection more challenging (Malware News).

Strategic Objectives of Stealth Falcon

Stealth Falcon’s operations, particularly in exploiting CVE-2025-33053, align with strategic objectives focused on intelligence gathering and surveillance. The group’s activities are primarily directed at defense and government organizations in the Middle East and Africa, highlighting a geopolitical dimension to their campaigns. The use of custom spyware implants like Horus Agent further indicates a targeted approach to infiltrating high-profile targets (UNDERCODE NEWS).

Conclusion

While this section discussed the technical aspects and implications of CVE-2025-33053, it is essential to recognize that the threat landscape is continually evolving. Organizations must remain vigilant and proactive in their cybersecurity measures to defend against sophisticated adversaries like Stealth Falcon.

Final Thoughts

The exploitation of CVE-2025-33053 by Stealth Falcon serves as a stark reminder of the persistent and evolving nature of cyber threats. By using living-off-the-land binaries and multi-stage loaders, the group effectively blends malicious activities with legitimate system operations, complicating detection efforts (Malware News). Organizations must remain vigilant, applying timely updates and employing advanced security measures to mitigate such risks. The strategic focus of Stealth Falcon on intelligence gathering in the Middle East and Africa further emphasizes the geopolitical dimensions of modern cyber warfare (UNDERCODE NEWS).

References

• National Vulnerability Database. (2025). CVE-2025-33053 Detail. NVD
• Bleeping Computer. (2025). Stealth Falcon Hackers Exploited Windows WebDAV Zero-Day to Drop Malware. Bleeping Computer
• Malware News. (2025). CVE-2025-33053: Stealth Falcon and Horus - A Saga of Middle Eastern Cyber Espionage. Malware News
• UNDERCODE NEWS. (2025). Stealth Falcon APT Exploits Microsoft RCE Zero-Day in the Middle East: A New Threat Emerges. UNDERCODE NEWS