CVE-2026-85880: Microsoft Windows Heap-Based Buffer Overflow Vulnerability

What it is

Microsoft Windows Advanced Local Procedure Call contains a heap-based buffer overflow vulnerability that allows an attacker to elevate privileges locally.

What to do

Schedule the vendor fix into this week’s change window, prioritising internet-facing and business-critical systems. Confirm the fix is applied everywhere, not just where it was easy.

Priority

This week: Schedule into this week’s change window.

Severity (CVSS)

7.8 high

CISA assessment (SSVC)

actively exploited; needs manual effort per target; total control of the affected system

Exploit probability (EPSS, 30 days)

3.6%, higher than 89% of all CVEs

Added to CISA KEV

8 September 2026

CISA fix-by date

22 September 2026 (US federal agencies; a sensible deadline for everyone)

Ransomware use

Not known

Weakness

CWE-122, CWE-908

References

• NIST NVD entry
• CISA KEV entry
• msrc.microsoft.com/update-guide/vulnerability/CVE-2026-85880
• www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-85880

Sources: CISA Known Exploited Vulnerabilities · FIRST Exploit Prediction Scoring System (EPSS) · NIST National Vulnerability Database · CISA Vulnrichment (SSVC), via the CVE Program. This product uses data from the NVD API but is not endorsed or certified by the NVD. Summaries are machine-written from CISA’s description; treat the vendor’s advisory as the authority for fixes.