SB2026051357 - Multiple vulnerabilities in Microsoft Office

Description

This security bulletin contains information about 4 vulnerabilities.

1) Use-after-free (CVE-ID: CVE-2026-40358)

CWE-ID: CWE-416 - Use After Free

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

The vulnerability allows a remote attacker to compromise vulnerable system.

The vulnerability exists due to a use-after-free error in Microsoft Office. A remote attacker can execute arbitrary code on the target system.

Successful exploitation of the vulnerability may allow an attacker to compromise vulnerable system.

2) Heap-based buffer overflow (CVE-ID: CVE-2026-42831)

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

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

The vulnerability allows a remote attacker to execute arbitrary code on the target system.

The vulnerability exists due to a boundary error in Microsoft Office. A remote attacker can trick a victim to open a specially crafted Office file, trigger a heap-based buffer overflow and execute arbitrary code on the target system.

Successful exploitation of this vulnerability may result in complete compromise of vulnerable system.

3) Heap-based buffer overflow (CVE-ID: CVE-2026-40363)

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

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

The vulnerability allows a remote attacker to execute arbitrary code on the target system.

The vulnerability exists due to a boundary error in Microsoft Office. A remote attacker can pass specially crafted data to the application, trigger a heap-based buffer overflow and execute arbitrary code on the target system.

Successful exploitation of this vulnerability may result in complete compromise of vulnerable system.

4) Improper access control (CVE-ID: CVE-2026-42832)

CWE-ID: CWE-284 - Improper Access Control

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

The vulnerability allows a local attacker to gain unauthorized access to otherwise restricted functionality.

The vulnerability exists due to improper access restrictions in Microsoft Office. A local attacker can bypass implemented security restrictions and perform spoofing attack on the system.

Remediation

Install update from vendor's website.

References

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-40358
• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-42831
• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-40363
• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-42832