Microsoft Defender prior 1.1.26060.3008 Malware Protection Engine 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.
8.4$0-$5k0.66

Summaryinfo

A vulnerability was found in Microsoft Defender. It has been rated as very critical. Affected by this issue is some unknown functionality of the component Malware Protection Engine. This manipulation causes integer underflow. This vulnerability is handled as CVE-2026-55011. It is possible to launch the attack on the local host. There is not any exploit available.

Detailsinfo

A vulnerability was found in Microsoft Defender. It has been declared as very critical. Affected by this vulnerability is an unknown function of the component Malware Protection Engine. The manipulation with an unknown input leads to a integer underflow vulnerability. The CWE definition for the vulnerability is 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. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

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

It is possible to read the advisory at msrc.microsoft.com. This vulnerability is known as CVE-2026-55011 since 06/16/2026. The exploitation appears to be easy. Attacking locally is a requirement. The technical details are unknown and an exploit is not publicly available. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 07/14/2026).

Upgrading to version 1.1.26060.3008 eliminates this vulnerability.

Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

Vendor

Name

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 8.8
VulDB Meta Temp Score: 8.4

VulDB Base Score: 8.8
VulDB Temp Score: 8.4
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: No

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

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Threat Intelligenceinfo

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

Countermeasuresinfo

Recommended: no mitigation known
Status: 🔍

0-Day Time: 🔒

Upgrade: Defender 1.1.26060.3008

Timelineinfo

06/16/2026 CVE reserved
07/14/2026 +28 days Advisory disclosed
07/14/2026 +0 days VulDB entry created
07/14/2026 +0 days VulDB entry last update

Sourcesinfo

Vendor: microsoft.com

Advisory: msrc.microsoft.com
Status: Confirmed

CVE: CVE-2026-55011 (🔒)
GCVE (CVE): GCVE-0-2026-55011
GCVE (VulDB): GCVE-100-378511

Entryinfo

Created: 07/14/2026 21:31
Changes: 07/14/2026 21:31 (52)
Complete: 🔍
Cache ID: 216::103

Be aware that VulDB is the high quality source for vulnerability data.

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