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CVE-2026-62877: Windows Win32k Elevation of Privilege Vulnerability

CVE-2026-62877 is a remote code execution vulnerability in Windows Win32k, rated Important by Microsoft, with a CVSS 3.1 base score of 7.8 (High). An attacker can exploit it by an attacker with local access, with low privileges and without user interaction. Microsoft has not reported exploitation in the wild and rates exploitation as less likely. The EPSS model estimates a 0.33% probability of exploitation activity in the next 30 days, higher than 27% of all scored vulnerabilities. Microsoft released the fix on 11 August 2026 in the August 2026 Patch Tuesday. It affects 4 products in 1 product family (Microsoft Office).

Key facts

CVE ID
CVE-2026-62877
Severity
High CVSS 7.8
Microsoft severity
Important
Impact
Remote Code Execution
Exploited in the wild
No
Publicly disclosed
No
Exploitation likelihood
Less Likely
Weakness
CWE-121
EPSS
0.33% (percentile 27%)
CISA KEV
Not listed
Released
Last updated
Patch Tuesday
August 2026 Patch Tuesday
Product families
Microsoft Office

CVSS score and vector

Microsoft scores CVE-2026-62877 at 7.8 (temporal 6.8) using CVSS 3.1. Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C

MetricValue
Attack vectorLocal
Attack complexityLow
Privileges requiredLow
User interactionNone
ScopeUnchanged
Confidentiality impactHigh
Integrity impactHigh
Availability impactHigh
Exploit code maturityUnproven
Remediation levelOfficial fix
Report confidenceConfirmed

Description

Stack-based buffer overflow in Windows Win32K allows an authorized attacker to elevate privileges locally.

Frequently asked questions (Microsoft)

What privileges could be gained by an attacker who successfully exploited this vulnerability?

An attacker who successfully exploited this vulnerability could gain SYSTEM privileges.

Affected products (4)

Microsoft Office

ProductSecurity updateTypeFixed buildRestart
Microsoft Office for AndroidRelease NotesSecurity Update16.0.20430.20000
Microsoft Office LTSC for Mac 2021Release NotesSecurity Update16.112.26090911
Microsoft Office LTSC for Mac 2024Release NotesSecurity Update16.112.26090911
Microsoft Office 365 for MacRelease NotesSecurity Update16.112.26090911

NIST NVD data

NVD status
Analyzed
NVD CVSS
7.8 (HIGH)
NVD weakness
CWE-121
Published to NVD
NVD last modified

Affected configurations (CPE)

ProductVulnerable versions
windows 10 1607 (x64)before 10.0.14393.9418
windows 10 1607 (x86)before 10.0.14393.9418
windows 10 1809 (x64)before 10.0.17763.9115
windows 10 1809 (x86)before 10.0.17763.9115
windows 10 21h2 (arm64)before 10.0.19044.7663
windows 10 21h2 (x64)before 10.0.19044.7663
windows 10 21h2 (x86)before 10.0.19044.7663
windows 10 22h2 (arm64)before 10.0.19045.7663
windows 10 22h2 (x64)before 10.0.19045.7663
windows 10 22h2 (x86)before 10.0.19045.7663
windows 11 23h2 (arm64)before 10.0.22631.7517
windows 11 23h2 (x64)before 10.0.22631.7517
windows 11 24h2 (arm64)before 10.0.26100.9106
windows 11 24h2 (x64)before 10.0.26100.9106
windows 11 25h2 (arm64)before 10.0.26200.9106
windows 11 25h2 (x64)before 10.0.26200.9106
windows 11 26h1 (arm64)before 10.0.28000.2704
windows 11 26h1 (x64)before 10.0.28000.2704
windows server 2012all listed versions
windows server 2012 r2all listed versions
windows server 2016before 10.0.14393.9418
windows server 2019before 10.0.17763.9115
windows server 2022before 10.0.20348.5440
windows server 2025before 10.0.26100.33222

References

Acknowledgments

  • Anonymous
  • Byzero with Kunlun Lab & Zhiniang Peng with HUST

Revision history

VersionDateDescription
1.0Information published.
2.0Added supported editions of Microsoft Office to the Security Updates table because they are affected by this vulnerability. Microsoft recommends that customers running any of these editions of Office install the latest security updates to be fully protected from this vulnerability.

Sources