CVE-2025-33073: Microsoft Windows SMB Client Improper Access Control Vulnerability

Should you act?

Exploited: patch now if you run it

CISA has confirmed exploitation in the wild. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• Yes, if you run Microsoft Windows. CISA added this CVE to its Known Exploited Vulnerabilities catalog on 2025-10-20, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2025-11-10; treat that as the outer limit, not the target.
• EPSS 82.7%, percentile 99.7: FIRST’s model estimates a 82.7% chance of exploitation activity in the next 30 days, higher than 99.7% of all scored CVEs (very high). EPSS is a probability, not a verdict.
• Needs an account (low (any account)). Exposure depends on who can log in.

What it is

Improper access control in Windows SMB allows an authorized attacker to elevate privileges over a network.

CISA’s summary

Microsoft Windows SMB Client contains an improper access control vulnerability that could allow for privilege escalation. An attacker could execute a specially crafted malicious script to coerce the victim machine to connect back to the attack system using SMB and authenticate.

Weakness type: CWE-284.

Product: Microsoft Windows · Assigned by: microsoft · Published: 2025-06-10

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Privileges required: low (any account)
• User interaction: none
• Scope: unchanged

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: added 2025-10-20; federal due date 2025-11-10. Known ransomware use: Unknown.
• CISA required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
• CISA SSVC assessment: exploitation active, automatable no, technical impact total.
• FIRST EPSS (model of 2026-10-21): 82.70% probability of exploitation activity in the next 30 days; percentile 99.7.

Timeline

• 2025-06-10 — CVE record published by microsoft
• 2025-10-20 — Added to CISA’s Known Exploited Vulnerabilities catalog
• 2025-11-10 — CISA remediation deadline for US federal agencies
• 2026-02-26 — CVE record last updated

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vendor and project advisories, patches

1. Windows SMB Client Elevation of Privilege Vulnerability msrc.microsoft.com
2. Listed in CISA KEV notes (msrc.microsoft.com) msrc.microsoft.com

Vulnerability records

1. CVE.org record CVE-2025-33073 cve.org
2. NVD entry CVE-2025-33073 nvd.nist.gov

Government

1. CISA Known Exploited Vulnerabilities catalog entry cisa.gov

Other references from the CVE record and advisory

1. vicarius.io vicarius.io
2. vicarius.io vicarius.io

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