CVE-2025-33073: Windows SMB Client Zero-Day Lets Attackers Gain SYSTEM Privileges
As the digital landscape continues to evolve in complexity, the number of discovered vulnerabilities is growing at an unprecedented pace, placing increasing pressure on cybersecurity teams. So far this year, NIST has recorded over 21,000 new CVEs, with experts projecting that number could reach 49,000+ by year’s end.
Given their widespread use, vulnerabilities affecting Microsoft products are among the most concerning. In its latest Patch Tuesday release, Microsoft addressed several disturbing ones, including a Windows Server Message Block (SMB) client elevation of privilege zero-day (CVE-2025-33073).
As vulnerability exploitation was the most common initial access vector for attackers in 2024, as per Mandiant’s M-Trends 2025 report, cyber defenders should remain vigilant, continuously monitoring for early signs of attack and defending proactively.
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CVE-2025-33073 Analysis
Among the 66 vulnerabilities addressed in this month’s Patch Tuesday release, CVE-2025-33073 stands out as particularly severe. This flaw affects the Windows Server Message Block (SMB) client and allows attackers to escalate privileges to the SYSTEM level on vulnerable devices.
The issue stems from improper access controls within the SMB protocol. According to Microsoft, an attacker with authorized access could craft a malicious script to trick a targeted machine into authenticating to a rogue SMB server. Successful exploitation grants the attacker SYSTEM-level privileges—effectively handing over full control of the compromised system.
Further, attackers can disable security tools, access sensitive data, install persistent malware, and move laterally within the network, posing a serious threat to enterprise environments. Given the widespread use of SMB in Windows networks, this vulnerability demands immediate patching. While a security update is now available and organizations are urged to apply it as soon as possible, the risk can also be mitigated by enabling server-side SMB signing through Group Policy.
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