SB2026021081 - Multiple vulnerabilities in Microsoft Windows Graphics Component

Description

This security bulletin contains information about 2 vulnerabilities.

1) Heap-based buffer overflow (CVE-ID: CVE-2026-21246)

CWE-ID: CWE-122 - Heap-based Buffer Overflow

CVSSv4: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear

The vulnerability allows a local user to escalate privileges on the target system.

The vulnerability exists due to a boundary error in Windows Graphics Component. A local user can pass specially crafted data to the application, trigger a heap-based buffer overflow and gain elevated privileges on the target system.

2) Use-after-free (CVE-ID: CVE-2026-21235)

CWE-ID: CWE-416 - Use After Free

CVSSv4: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear

The vulnerability allows a local user to escalate privileges on the system.

The vulnerability exists due to a use-after-free error in Windows Graphics Component in win32kfull driver. A local user can execute arbitrary code with SYSTEM privileges. 

Remediation

Install update from vendor's website.

References

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21246
• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21235
• https://www.zerodayinitiative.com/advisories/ZDI-26-081/