Feb 2026: Microsoft Excel Information Disclosure Vulnerability
CVE-2026-21258 Published on February 10, 2026
Microsoft Excel Information Disclosure Vulnerability
Improper input validation in Microsoft Office Excel allows an unauthorized attacker to disclose information locally.
Weakness Types
Improper Input Validation
The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.
Out-of-bounds Read
The software reads data past the end, or before the beginning, of the intended buffer. Typically, this can allow attackers to read sensitive information from other memory locations or cause a crash. A crash can occur when the code reads a variable amount of data and assumes that a sentinel exists to stop the read operation, such as a NUL in a string. The expected sentinel might not be located in the out-of-bounds memory, causing excessive data to be read, leading to a segmentation fault or a buffer overflow. The software may modify an index or perform pointer arithmetic that references a memory location that is outside of the boundaries of the buffer. A subsequent read operation then produces undefined or unexpected results.
Products Associated with CVE-2026-21258
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Affected Versions
Microsoft 365 Apps for Enterprise:- Version 16.0.1 and below https://aka.ms/OfficeSecurityReleases is affected.
- Version 16.0.0.0 and below 16.0.5539.1002 is affected.
- Version 19.0.0 and below https://aka.ms/OfficeSecurityReleases is affected.
- Version 16.0.1 and below https://aka.ms/OfficeSecurityReleases is affected.
- Version 16.0.0 and below https://aka.ms/OfficeSecurityReleases is affected.
- Version 16.0.1 and below 16.106.26020821 is affected.
- Version 16.0.0 and below 16.106.26020821 is affected.
- Version 16.0.0.0 and below 16.0.10417.20097 is affected.
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.