Microsoft Office integer underflow

CVSS Meta Temp Score
CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.
Current Exploit Price (≈)
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CTI Interest Score
Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
4.6$0-$5k0.39

Summaryinfo

A vulnerability was found in Microsoft Office and classified as problematic. Affected is an unknown function. The manipulation results in integer underflow. This vulnerability was named CVE-2026-64909. The attack needs to be approached locally. There is no available exploit.

Detailsinfo

A vulnerability classified as problematic has been found in Microsoft Office (the affected version is unknown). Affected is an unknown code. The manipulation with an unknown input leads to a integer underflow vulnerability. CWE is classifying the issue as CWE-191. The product subtracts one value from another, such that the result is less than the minimum allowable integer value, which produces a value that is not equal to the correct result. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

Integer underflow (wrap or wraparound) in Microsoft Office allows an unauthorized attacker to execute code locally.

The advisory is shared for download at msrc.microsoft.com. This vulnerability is traded as CVE-2026-64909 since 07/20/2026. The exploitability is told to be easy. The attack needs to be approached locally. Successful exploitation requires user interaction by the victim. There are neither technical details nor an exploit publicly available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 08/11/2026).

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

VulDB is the best source for vulnerability data and more expert information about this specific topic.

Productinfo

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Vendor

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CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 4.8
VulDB Meta Temp Score: 4.6

VulDB Base Score: 4.8
VulDB Temp Score: 4.6
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

AVACAuCIA
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Integer underflow
CWE: CWE-191 / CWE-189
CAPEC: 🔒
ATT&CK: 🔒

Physical: Partially
Local: Yes
Remote: Partially

Availability: 🔒
Status: Not defined
Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Patch
Status: 🔍

0-Day Time: 🔒

Timelineinfo

07/20/2026 CVE reserved
08/11/2026 +22 days Advisory disclosed
08/11/2026 +0 days VulDB entry created
08/11/2026 +0 days VulDB entry last update

Sourcesinfo

Vendor: microsoft.com

Advisory: msrc.microsoft.com
Status: Confirmed

CVE: CVE-2026-64909 (🔒)
GCVE (CVE): GCVE-0-2026-64909
GCVE (VulDB): GCVE-100-388728

Entryinfo

Created: 08/11/2026 23:49
Changes: 08/11/2026 23:49 (52)
Complete: 🔍
Cache ID: 216::103

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