SB20260113102 - Multiple vulnerabilities in Microsoft Excel
Published: January 13, 2026
Breakdown by Severity
- Low
- Medium
- High
- Critical
Description
This security bulletin contains information about 6 secuirty vulnerabilities.
1) Untrusted Pointer Dereference (CVE-ID: CVE-2026-20955)
The vulnerability allows a remote attacker to execute arbitrary code on the target system.
The vulnerability exists due to untrusted pointer dereference in Microsoft Excel. A remote attacker can trick a victim to open a specially crafted file and execute arbitrary code on the system.
2) Improper access control (CVE-ID: CVE-2026-20949)
The vulnerability allows a remote attacker to gain unauthorized access to otherwise restricted functionality.
The vulnerability exists due to improper access restrictions in Microsoft Excel. A remote attacker can trick a victim to open the malicious workbook, enable editing and then click the attacker‑supplied Quick Access Toolbar (QAT) button to bypass a security feature.
3) Use-after-free (CVE-ID: CVE-2026-20950)
The vulnerability allows a remote attacker to compromise vulnerable system.
The vulnerability exists due to a use-after-free error in Microsoft Excel. A remote attacker can trick a victim to open a specially crafted file and execute arbitrary code on the target system.
4) Integer underflow (CVE-ID: CVE-2026-20957)
The vulnerability allows a remote attacker to execute arbitrary code on the target system.
The vulnerability exists due to integer underflow in Microsoft Excel. A remote attacker can trick a victim to open a specially crafted file, trigger integer underflow and execute arbitrary code on the target system.
Successful exploitation of this vulnerability may result in complete compromise of vulnerable system.
5) Out-of-bounds read (CVE-ID: CVE-2026-20946)
The vulnerability allows a remote attacker to gain access to potentially sensitive information.
The vulnerability exists due to a boundary condition in Microsoft Excel. A remote attacker can create a specially crafted file, trick the victim into opening it, trigger an out-of-bounds read error and read contents of memory on the system, leading to arbitrary code execution.
6) Untrusted Pointer Dereference (CVE-ID: CVE-2026-20956)
The vulnerability allows a remote attacker to execute arbitrary code on the target system.
The vulnerability exists due to untrusted pointer dereference in Microsoft Excel. A remote attacker can trick a victim to open a specially crafted file and execute arbitrary code on the system.
Remediation
Install update from vendor's website.
References
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20955
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20949
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20950
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20957
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20946
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20956