Microsoft Office Excel heap-based overflow

Summaryinfo

A vulnerability described as problematic has been identified in Microsoft Office. Affected is an unknown function of the component Excel. The manipulation results in heap-based overflow. This vulnerability is cataloged as CVE-2026-56156. The attack must be initiated from a local position. There is no exploit available.

Detailsinfo

A vulnerability, which was classified as problematic, was found in Microsoft Office (unknown version). Affected is an unknown code block of the component Excel. The manipulation with an unknown input leads to a heap-based overflow vulnerability. CWE is classifying the issue as CWE-122. 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(). This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

Heap-based buffer overflow in Microsoft Office Excel allows an unauthorized attacker to execute code locally.

The advisory is available at msrc.microsoft.com. This vulnerability is traded as CVE-2026-56156 since 06/19/2026. The exploitability is told to be easy. Local access is required to approach this attack. Successful exploitation requires user interaction by the victim. The technical details are unknown and an exploit is not available. The structure of the vulnerability defines a possible price range of USD $5k-$25k at the moment (estimation calculated on 07/15/2026).

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

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Productinfo

Type

• Office Suite Software

Vendor

• Microsoft

Name

• Office

License

• commercial

Website

• Vendor: https://www.microsoft.com/

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