High Severity Vulnerability
This vulnerability has been rated as High severity. Immediate action is recommended.
CVE-2026-20957
High
Low
Medium
High
Critical
7.8
CVSS Score
Vulnerability Description
Integer underflow (wrap or wraparound) in Microsoft Office Excel allows an unauthorized attacker to execute code locally.
CVSS Metrics
Common Vulnerability Scoring System
Vector String:
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Attack Vector
L
Attack Complexity
L
Privileges Required
N
User Interaction
R
Scope
U
Confidentiality
H
Integrity
H
Availability
H
Known Affected Software
5 configuration(s) from 1 vendor(s)
office_long_term_servicing_channel
Version:
2024
CPE:
cpe:2.3:a:microsoft:office_long_term_servicing_channel:2024:*:*:*:*:-:x64:*
office_long_term_servicing_channel
Version:
2021
CPE:
cpe:2.3:a:microsoft:office_long_term_servicing_channel:2021:*:*:*:*:*:x86:*
office
Version:
2019
CPE:
cpe:2.3:a:microsoft:office:2019:*:*:*:*:-:x64:*
excel
Version:
2016
CPE:
cpe:2.3:a:microsoft:excel:2016:*:*:*:*:mac_os_x:*:*
365_apps
Version:
-
CPE:
cpe:2.3:a:microsoft:365_apps:-:*:*:*:enterprise:*:x64:*
This vulnerability affects 5 software configuration(s). Ensure you patch all affected systems.
Severity Details
7.8
out of 10.0
High
Weakness Type (CWE)
CWE-122
Heap-based Buffer Overflow
- Description
- A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc().
- Exploit Likelihood
- High
- Typical Severity
- High
- Abstraction Level
- Variant
Key Information
- Published Date
- January 13, 2026
