CVE-2025-59287: Microsoft Windows Server Update Service (WSUS) Deserialization of Untrusted Data 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 2025-10-24, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2025-11-14; treat that as the outer limit, not the target.
• EPSS 100.0%, percentile 100.0: FIRST’s model estimates a 100.0% chance of exploitation activity in the next 30 days, higher than 100.0% of all scored CVEs (very high). EPSS is a probability, not a verdict.
• Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
• Editorial verdict: Patch this week. Microsoft WSUS CVE-2025-59287: Unauthenticated SYSTEM RCE — Only servers with the WSUS role are at risk, but on those it is unauthenticated SYSTEM code execution: patch them now, and treat any WSUS server exposed on 8530/8531 to the internet as a likely incident.

What it is

Deserialization of untrusted data in Windows Server Update Service allows an unauthorized attacker to execute code over a network.

CISA’s summary

Microsoft Windows Server Update Service (WSUS) contains a deserialization of untrusted data vulnerability that allows for remote code execution.

Weakness type: CWE-502.

Product: Microsoft Windows · Assigned by: microsoft · Published: 2025-10-14

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Privileges required: none (no login)
• 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 2025-10-24; federal due date 2025-11-14. 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 yes, technical impact total.
• FIRST EPSS (model of 2026-10-21): 99.98% probability of exploitation activity in the next 30 days; percentile 100.0.

Timeline

• 2025-10-14 — CVE record published by microsoft
• 2025-10-23 — erroneo.us brief: Microsoft WSUS CVE-2025-59287: Unauthenticated SYSTEM RCE
• 2025-10-24 — Added to CISA’s Known Exploited Vulnerabilities catalog
• 2025-11-14 — 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 Server Update Service (WSUS) Remote Code Execution Vulnerability msrc.microsoft.com
2. Listed in CISA KEV notes (msrc.microsoft.com) msrc.microsoft.com

Vulnerability records

1. CVE.org record CVE-2025-59287 cve.org
2. NVD entry CVE-2025-59287 nvd.nist.gov

Government

1. CISA Known Exploited Vulnerabilities catalog entry cisa.gov

Other references from the CVE record and advisory

1. gist.github.com gist.github.com
2. bleepingcomputer.com bleepingcomputer.com
3. hawktrace.com hawktrace.com
4. vicarius.io vicarius.io
5. vicarius.io vicarius.io

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